This notification appeared every day after I got my shiny-new / soon-to-be-obsolete Google Pixel XL:

Screenshot_20170906-085931 – Update Your Phone Number – detail

Fast-forward through nearly a month of doing the obvious things to no avail:

• Tap the notification to update my phone number
• Update my phone number from Firefox on the Pixel
• Update my phone number from Firefox on my desktop
• Ditto, from Chromium
• Just dismiss the notification, repeatedly
• Change my phone number in various Google places
• Ditto, in various ways

Searching on the obvious keywords provided very few hits and none with a resolution. I followed one suggestion to flush the Google Play and Google Play Services caches, to no visible effect.

So I started a chat with Google Support by coredumping the entire list of Things Already Tried. After ten minutes of pleasantries, mostly spent idling while Holmes (great name for a tech support guy) read my coredump (and, most likely, timeshared a dozen other support chats), this transpired:

11:36:01​ ​ Holmes:​ ​ I ​ ​ see​ ​ that​ ​ you’ve​ ​ tried​ ​ almost​ ​ all​ ​ the​ ​ things​ ​ to​ ​ get​ ​ rid​ ​ of​ ​ the​ ​ notification​ ​ for​ ​ Google​ ​ play services.
11:36:05​ ​ Holmes:​ ​ Is​ ​ that​ ​ right?
11:36:57​ ​ Ed​ ​ Nisley:​ ​ It’s​ ​ everything​ ​ I ​ ​ could​ ​ think​ ​ of,​ ​ plus​ ​ a ​ ​ bit​ ​ of​ ​ searching​ ​ the​ ​ usual​ ​ forums.​ ​ A ​ ​ few​ ​ other folks​ ​ have​ ​ the​ ​ same​ ​ problem,​ ​ but​ ​ none​ ​ have​ ​ a ​ ​ resolution.
11:38:04​ ​ Holmes:​ ​ Sure,​ ​ I ​ ​ understand​ ​ that.​ ​ Please​ ​ don’t​ ​ worry​ ​ at​ ​ all,​ ​ we’ve​ ​ a ​ ​ dedicated​ ​ team​ ​ of​ ​ experts​ ​ for Play​ ​ related​ ​ concern.​ ​ I’m​ ​ from​ ​ hardware​ ​ nexus​ ​ Support​ ​ team.
11:38:15​ ​ Holmes:​ ​ I’d​ ​ connect​ ​ you​ ​ directly​ ​ with​ ​ them.

I’ve never gotten to Level 2 that fast in my entire life!

Fifteen minutes later (again, mostly his reading & timesharing):

11:54:37​ ​ Calvin​ ​ S:​ ​ The​ ​ issue​ ​ might​ ​ be​ ​ due​ ​ to​ ​ some​ ​ residual​ ​ files​ ​ that​ ​ might​ ​ hinder​ ​ the​ ​ download​ ​ process.
Lets​ ​ try​ ​ to​ ​ clear​ ​ cache​ ​ of​ ​ Google​ ​ Play​ ​ Store,​ ​ to​ ​ see​ ​ if​ ​ the​ ​ issue​ ​ can​ ​ be​ ​ resolved.
11:55:06​ ​ Calvin​ ​ S:​ ​ I ​ ​ can​ ​ help​ ​ you​ ​ with​ ​ the​ ​ steps,​ ​ if​ ​ you​ ​ want​ ​ to.
11:55:10​ ​ Ed​ ​ Nisley:​ ​ As​ ​ I ​ ​ said​ ​ in​ ​ the​ ​ initial​ ​ description,​ ​ I’ve​ ​ already​ ​ done​ ​ that.
11:55:39​ ​ Calvin​ ​ S:​ ​ I ​ ​ appreciate​ ​ your​ ​ efforts​ ​ to​ ​ fix​ ​ this​ ​ issue.
11:56:08​ ​ Ed​ ​ Nisley:​ ​ Blew​ ​ away​ ​ all​ ​ the​ ​ caches​ ​ for​ ​ anything​ ​ to​ ​ do​ ​ with​ ​ Google​ ​ Play​ ​ anything!
11:56:20​ ​ Calvin​ ​ S:​ ​ Could​ ​ you​ ​ please​ ​ let​ ​ me​ ​ know,​ ​ what​ ​ all​ ​ troubleshooting​ ​ steps​ ​ you​ ​ have​ ​ tried?
11:57:05​ ​ Ed​ ​ Nisley:​ ​ Did​ ​ you​ ​ read​ ​ the​ ​ initial​ ​ description​ ​ I ​ ​ sent​ ​ to​ ​ start​ ​ this​ ​ chat?​ ​ Took​ ​ Holmes​ ​ five​ ​ minutes to​ ​ chew​ ​ through​ ​ it.
11:58:11​ ​ Calvin​ ​ S:​ ​ I ​ ​ see​ ​ that​ ​ you​ ​ have​ ​ cleared​ ​ cache​ ​ of​ ​ Play​ ​ services.
11:58:50​ ​ Calvin​ ​ S:​ ​ Let​ ​ us​ ​ uninstall​ ​ updates​ ​ for​ ​ the​ ​ Play​ ​ Store​ ​ app​ ​ Play​ ​ Store​ ​ and​ ​ Google​ ​ Play​ ​ Services.

At which point it became obvious I was going to spend the rest of the day dinking around:

12:00:58​ ​ Ed​ ​ Nisley:​ ​ Given​ ​ that​ ​ this​ ​ notification​ ​ appears​ ​ in​ ​ the​ ​ morning,​ ​ doing​ ​ this​ ​ step​ ​ by​ ​ step​ ​ will​ ​ take days.​ ​ Give​ ​ me​ ​ a ​ ​ list​ ​ of​ ​ everything​ ​ you​ ​ will​ ​ suggest​ ​ so​ ​ I ​ ​ can​ ​ do​ ​ it​ ​ without​ ​ wasting​ ​ hours​ ​ typing​ ​ at​ ​ you.
12:02:22​ ​ Calvin​ ​ S:​ ​ Respecting​ ​ your​ ​ time,​ ​ I’ll​ ​ follow​ ​ up​ ​ with​ ​ you​ ​ over​ ​ an​ ​ email​ ​ with​ ​ all​ ​ the​ ​ possible troubleshooting​ ​ steps.

The “troubleshooting steps” look like a generic list of progressively more desperate measures applicable to any mysterious Android problem:

Clear app data for the Play Store

Go to Settings > Apps.
Tap Google Play Store > Storage > Clear data > Ok.
At the top left, tap the Back arrow to go to the “App info” screen.
At the top right, tap More (3 dots) > Uninstall updates > Ok > Ok to restore the app to its factory version.
Note: The Play Store will update automatically within 48 hours. If “Uninstall updates” is dimmed, you can skip this step.
Note: If you’ve changed the Google Play Store app settings (content filters, password protection, etc.), you’ll need to set them up again.

Clear the app data of Google Play services

Warning: Clearing the app data of Google Play services can reset settings, affect app performance, and cause unpredictable behavior across the device.

Go to Settings > Apps or Application Manager.
At the top right, tap More (3 dots) > Show system apps (on Android versions lower than 6.0, go to All instead).
Tap Google Play services.
Note: If you don’t see “Google Play services,” check Show all system apps and make sure that both Google Play Framework and Google Play Services are enabled. ​​If they aren’t enabled, download the Google Play Service from Play Store.
Tap Storage > Clear cache.
Then tap Manage Space > Clear All Data > Ok.

After completing this step, you should check the settings on your apps to see if they’re still configured correctly.

Remove and re-add your Google Account

Note: This may reset settings and remove in-app content. However, your purchases and synced data (Gmail, Google contacts, etc.) are tied to your account and will be available after re-adding your account.

Go to Settings > Accounts > Google.
Tap the name of the account you wish to remove.
Important: Make sure you remember your account password. You’ll need it to sign back in to your account.
At the top right, tap More (3 dots) > Remove account > Remove account.
At the top left, tap the Back arrow > Add account > Google.
Sign in to your Google Account.

Uninstall and reinstall Play Store updates

Temporarily uninstalling updates to the Google Play Store app can help fix some issues.

To revert the Play Store app to the previous version:

Go to Settings.
Tap Apps or Application manager (depending on the device).
Tap Google Play Store (depending on the device, you may need to go to All).
Tap on the menu button, and then Uninstall updates.
If the Uninstall updates button isn’t available, skip the rest of this step and continue troubleshooting.
When prompted to change the Play Store app back to the factory version, tap OK.
Go back to the device’s home screen and relaunch the Play Store. Your Play Store app should update to the latest version within a few minutes.
If the Play Store app doesn’t update, tap on the menu button from within the app and go to Settings. Scroll down until you see Play Store Version. Tap on that to check for an update. If none is available, continue to the next step.

Uninstall updates for Google Play Services

Go to Settings.
Tap Apps or Application manager (depending on the device).
Tap Google Play Services (depending on the device, you may need to go to All).
Tap on the menu button, and then Uninstall updates.
If the Uninstall updates button isn’t available, skip the rest of this step and continue troubleshooting.
When prompted to change the Play Store app back to the factory version, tap OK.

Reset your device to factory settings

If you’d like help with resetting your device, contact us from another device and we’ll walk you through it.

To reset your device:

If you have an SD card, remove it to save the data on the card.
Reset your Android device to factory settings.
Sign in to your device with a Google Account that was signed in before the reset.
If you removed an SD card, reinsert it.

To reload your apps and data:

Open the Play Store app.
Tap the Menu (3 lines) > My apps & games > Library.
Next to the apps that you’d like to install, tap Install or Enable.

If the issue still persist after performing all the troubleshooting steps I request you to reply to this email with the screenshot.

As it turned out, blowing away “the app data of the Google Play services” did the trick; the notification Went Away and hasn’t returned.

I hope I never need that information again …