changed appleID email - can't login to anything on MacBook

I changed my AppleID email address to a new email address (old one was overrun with spam). The AppleID password is fine, and works on everything on my iPhone as well as iCloud on the web (accessing via same device that is giving me trouble.)

In the settings on my MacBook, it still displays the old email address as my AppleID, and prompts me to enter the password (which I repeat works everywhere else).

Obviously entering the password on the MacBook does not work, but without it working, I cannot get into settings to update the AppleID email address I'm now using.

It's a vicious cycle of dysfunction. SOS!

Thanks in advance!