Hmmmm Interesting never seen that bug before.
Another 2 questions I have,
- Did you create the account in FNC? or did someone else Upgrade it to UEFN and move it to a team of yours
- Are your island slots filled in FNC? maybe you are full of islands and it can’t convert?
If you made it on your account and have slots in FNC I would recommend getting a video of the bug and posting a bug report here Epic Developer Community Forums