Pixal 4a OTA to 2.0 seems to not work even though it says it is available

I have not found a fix for my original problem and seeing as there have been issues with trying to fix it, you need to take into account that a solution might not be found. I think that if you want/need security updates and everything, you need to consider backing up your files and apps, and do a complete new install with the latest version. That might be your fastest solution.