okay, this is what you do:
Boot into Safe mode (either boot into Android and hold restart option or turn phone off, hold power button until you see Google Logo, when you see it, let go of power and hold Volume Down button)
Now disable Bluetooth and enable Wifi (it will be disabled so make sure you do this). Then force stop Play Store app. Long-press on shortcut, my apps, update all. Make sure you do these steps exactly as written.
Then open
this link in Google Chrome (must be opened in your default browser so it opens the hidden Play Services app in Google Play Store), it will open Google Play Services. hit update, it takes 45 seconds to install in the background.
While that is updating, go to Android Settings, Security and update both System Security and Play System. Now restart your phone.
I've helped approximately 8 or 9 users on reddit in December and January with this method so hopefully that works.
I also had this issue in December after updating the December Update. The only way I could fix it was by using the Android Flash Tool and installing the November Factory Image (not OTA) and picking wipe phone and flash all partitions. read on...
Try the Official Android Flash Tool (link below), on that page hit the "pencil" and you will see advanced options - check the boxes for "Wipe Device" and "Flash All Partitions" (no need to relock the bootloader just yet until you fix your phone).
If you are using windows, download the latest Google USB driver file from the link below), extract the file and right-click on the Android_winusb.inf file and hit "install". Now when you are using the Official Flash Tool website or command line, make sure you are in the Bootloader Menu (Fastboot Screen) where it says "Device State: Locked/Unlocked" and you have the options to boot into recovery/rescue mode etc. That's the Bootloader (looks like you've flashed the image already but maybe it didn't work so using the Android Flash tool is recommended). For the Flash Tool, you'll need to use Google Chrome and also disable adblockers and don't use incognito mode during the process.
USB Drivers for Google Devices:
The Google USB Driver is required for Windows if you want to perform adb debugging with Google devices.
developer.android.com
Android Flash Tool:
flash.android.com
You can also go to the
Android Factory Image Download Page, and try a different Build from October or November. Do that by clicking the blue "Flash" word (not the link to downlod) beside the Build Number which will also take you to the Android Flash Tool website (the Android Flash Tool has two different pages which do the same thing, back-to-public and the direct "Flash" page for a specific build). For example, under the Pixel 6 Pro, for November, there's a build Number
12.0.0 (SP1A.211105.003, Nov 2021) and beside that you can flash the image using the Android Flash Tool or download the full image like you've previously done.