Organization membership invitation failed

I am trying to send organization membership invitation to users. The error message that we got is Failed Invitation Accept - the specified account is not allowed to accept the current invitation

Please advise. Thanks in advance.

Hey there!

Are you able to provide us with any additional context on that front? It would be great if you can send me a private message here in the forum with the captured flow of inviting that user in a form of HAR file: