Hi MAJackie,
Thank you so much for your post and sorry to hear that you were not able to add another user. I'd be glad to take a look at this for you. Can you please confirm if it is happening for all company file when you try to add another user? If not, can you please reply what Company File ID you are having issues in adding another user?
Looking at the email that is linked to your account it's already the File owner/Primary Contact. I've also refreshed something on the back ends please do let me know if your still having issues.
Regards,
Earl