[Google Pixel 2 XL Questions & Answers] simplepinoi177:
I think I figured it out....[GUIDE] included!

I think I figured it out (at least in my case) -- but I think it's probably applicable to most any other(s) who are having the same issue...

First of all, if you have Titanium Backup, make sure to set Default auto-update app to Enabled

Go to Menu

Preferences

Go to Restoration Settings

You will find Default auto-update mode in the section; 4th on the list within that section

Go to Google Play Store App Info

Clear Cache (inside Storage)

Clear Data (also inside Storage)

Disable the app

Click OK when warned that it will "replace this app with the factory version..."

Go to Settings, Apps & Notifications, See all ### apps

At the top right, select the 3 verticle dots and select "Show system"

Find and select Google Play Services

Clear Cache

Go back to App Info (back arrow; arrow pointing left), at the top right, select the 3 vertical dots and select "Uninstall updates"

Click OK when warned that it will "replace with the factory version..."

Reboot

Download the latest Google Play Services

HERE'S one place you can find it and/or you can Google search to find other copies yourself...

Pick the newest latest version (beta if you wish to be on bleeding edge but stability not ensured)

Choose the Android 8.0+ variant

Download the "arm64 + arm" & "nodpi" one

Install the latest Google Play Services using the file you downloaded

Reboot

Go back to Google Play Services App Info (show all ### apps, show system, etc.)

Clear Cache (of Google Play Services)

Go back to "show all ### apps"

Select the drop-down menu and select Disabled

Select Google Play Store

Clear Cache and Data (of Google Play Store inside Storage)

Plug Phone to charger

Launch Google Play Store

Select the 3 stacked horizontal lines on the top left and go to Settings

Select and configure how you wish to auto-update apps

Click on Play Store version (all the way on the bottom)

After pressing OK (it'll most likely say Play Store will update soon), it may or may not begin downloading components for the Play Store. After a bit, it may or may not actually begin auto-updating...

In the few instances I've done this and on the 2 pixel 2's I have access to, the auto-updating may begin soon after (within 2 minutes), or eventually (sorry for vague description, but I had thought these steps didn't work and wasn't paying attention and after a while, I saw it auto-updating!).

Also, it still seems that it'll auto-update only while plugged in charging. That particular bug/requirement hasn't been resolved, but as this is specifically an auto-update troubleshooting thread.......

Hope this helps any/all who is having the same issue. I hope (but am doubtful) that this will work for everyone; but if it doesn't, I'd have to say that it might be something with your ROM (stock or custom), settings (system or another app interfering [As I found out TB actually might/does]), or some very unique bug because this is probably the most comprehensive app reset for Google Play. It's kind of overkill, but you might have some luck going the "last resort" route and flashing the Full Factory image in hopes it'll fix the system and app comparability issues (if that is indeed the reason...).

In the end, I hope this helps any who might be having this issue....:victory::highfive: