Added second address and back-up - problems

I added a second address a week or so ago. Firstly I can only seem to receive mail on the new address.

But most importantly, when the second address was up and running, my Inbox disappeared, but with Sent, Drafts folders as before.

I’ve tried running backups and they are are large as before. Until yesterday the back-up file had “zipped” or something similar in the title. I’ve just made another back-up and it doesn’t have “zipped” in the title.

Previously I think I successfully unzipped the file using “Extract all” in Windows 11.

When I go to Menu/File/Import I can’t find the file, although it is there in Windows Explorer, timed at 15 mins ago.

I am desperate to get the Inbox backed-up with 2 days as I am moving to a Mac on Friday.

Can anybody help?