(login is broken) Can't access from Tapatalk

Hi,
 
For years I've occasionally but repeatedly used Tapatalk to check the forum from my Android devices (tablet and smartphone).
 
As from yesterday I can no longer access the forum and get from the program the following message:
"Failed to connect to forum, please check with the forum administrator if this problem persists",
As said, it's not a logon problem, but an access problem.
 
To help identifying the cause I add that Tapatalk works fine with other forums, and the same issue exists from two different Android devices.
 
Thanks,
 
edborg