Grandstream became unregistered after running firewall checker on 3CX

[Stephen H]

Greetings, with a Grandstream HT841 running fine for months, i ran the firewall checker on my 3CX v20 and now it will not re-register. I verified my SIP user ID, the Authentication ID and the Auth Password as well as the SIP server address. Any idea what might have caused this issue? Is there any more information that i could provide? Any help at all would be greatly appreciated