Unfortunately, I have not fixed the issue. I tried to get help from X1 tech support, but they say that they just don't support ARM. It is a horrible shame, as all my others Win 11 (Intel) applications work just fine on Parallels Win 11 on Mac silicon. Its not clear why X1 won't work.
My most recent solution is to buy a small form factor Windows PC for the sole purpose of running Intel Windows & Outlook & X1, and then I connect via RDP to have an x1 window in my Mac's desktop. But this is a poor substitute.
I have been trying to force myself to get used to Mac's spotlight search, since getting X1 on Mac is just a losing battle. There is a convenient native Mac application called HoudahSpot that provides a reasonable interface to Spotlight, but not as elegant as X1's. So far, I've been able to use HoudahSpot to search all my emails and all my Mac's file content. I have not, though, been able to confirm whether I can search the content of mail attachments. Be aware that if you want HoudahSpot to be able to search your emails, you MUST use the native MacOS mail application, and not Outlook (or you can run both, but spotlight, and therefore HoudahSpot, only connects to the mail content retrieved by MacOS mail).
I have been asking X1 support for literally years to consider porting X1 to MacOS, but they always have higher priorities.