App-Specific Password problems

Hi there, I’ve got a problem signing into iCloud via apps that require an app-specific password to login; namely Outlook and/or Windows 10 Mail.

Background info for relevance (if any) - I have an older .mac era account and I’m also the family organiser for 4 other accounts.

Trying to set up iCloud on Outlook for iPad with my regular iCloud password yields the following message:

“Unable to log in. Please check your email address and password and try again. 2-factor authentication is now required for this account, you might need to create an app-specific password before continuing.”

So I go to the AppleId website and request a new app-specific password, copy it into Outlook and the exact same message displays. Several different app-specific passwords requested and copy/pasted, but none work.

Same/similar situation with Windows 10 mail app, whether with an app-specific password or my regular one. The strange thing is though, when adding my wife’s account (who was a .me-era adopter), her app-specific password works fine.

I do have other minor 2FA gremlins - such as the location shown (when logging in via another device) being completely wrong, and I don’t use a VPN (probably should!)...so is it maybe just a backward compatibility issue with older accounts? That strikes me as being far-fetched when everything else works as it should.

Any help from would be greatly appreciated!