"your password is required to enable iCloud Photo Library"

I just bought the Macbook Pro 16" and I am soooo frustrated with how NOTHING works. My migration assistant got hung up and I had to stop it, erase the content and reinstall the Catalina OS, which did NOT work until I fiddled around with a bunch of settings in Recovery mode. I don't even know all that I did.

Then, it took me 2 nights to realize I had 3 "MacIntosh HD" drives listed in finder. Recovery mode again, disk utility, this time somehow the drive name got lost in the shuffle and it was back to its factory name, no "McIntosh HD." Figured my way around that, somehow ended up with 2 user accounts one of which is not on the source computer nor did I set it up on the new machine. Deleted the one mystery user, then moved its content to Trash, and couldn't empty Trash. There were hundreds of filenames that popped up saying "xxxx is a system file needed by macOS. Do you want to erase?" But there were NO system files in the folder for the deleted user on the Trash file list that I could see.

Reran migration assistant, looked like everything came back ok, even the Trash was empty. But NOW, when I go to "About this Mac," then select "Storage" and "Manage", The next display that comes up allows you to select "Store in iCloud". When I select that, I get this message:

"Your password is required to enable iCloud Photo Library" Open Apple ID in System Preferences to turn on iCloud Photo Library". Thing is, I AM logged into iCloud already on this machine. When I go to System Preferences, "Photo Library" is already selected.

This whole fiasco is bad enough to make me want to return the thing, except that my old one is old.

I've rebooted and the problem is still there. And the Photo Library is populated from my iCloud account. Any suggestions as to what is going on?

Anyone else successfully migrate from another macbook pro? (Mine is a mid 2013 running Catalina).