User sign in via invite link gets the following error

I have a free host for 10 users, tried to create a demo site for showing the app before moving to the paid plan. The user coming by invite link gets an error after verifying the email address. After the page reload he seems to have access, but I doubt that he will continue after the error.

Cannot report a ticket as a bug as a host is using the free plan. What’s next?

Sincerely, Vadim