MacMail Archive Command Returns Error "Could Not be Moved to the Mailbox (Null)"

Hello, I'm unable to archive messages for my outlook.com email account in Mac Mail - using the archive command. It works for other exchange accounts. And it works on my iPad and iPhone. Have read previous threads and tried to follow them, but they don't apply exactly:

Archive command not working Apple Mail in… - Apple Community.

The Archive button exists - but doesn't work

An error occurred while moving messages t… - Apple Community

Same message text but moving to Trash rather than Archive. But outdated. The command doesn't exist in the mailbox menu.

Finally, I've looked in Mailbox behaviors in settings and do not see an option to set the archive folder.

Here's the error message: implies the archive folder doesn't exist. Yet, it does. What am I missing? How does someone manually tell Mac Mail where to archive? Is there a text (config) file that needs edited?