Formstack App - "Error: Sorry, but this account has not been verified!"

Hi! I want to use the Formstack app, but I’m getting this error when I hit the “Create document” button:

Similarly, in Formstack, the Merge History shows:

I’m signed in to both applications and am not having any other problems in either of them, but something about the integration is obviously not right. I haven’t seen this problem discussed in other posts - has anyone else seen this behavior? Not sure what to try!