Users cannot login in their Messenger accounts. That was working fine and stopped suddenly.
A reason behind is a recent bug in gwadminservice part of the GroupWise which is currently under investigation.
A condition under which this problem happens is when the LDAP feature of MTA is not secured. Using that configuration has been working before.
Since the cause is clear, you must activate on the MTA LDAP the SSL settings and the set some not yet used port value, if 636 might be already occupied by, for instance, eDir service.
You can leave "Use the MTA Certificate and Key" option set if your MTA has under SSL Settings valid certificate info. If those key and certificate fields on the MTA are empty, click on "Generate Certificate" button and set some password.
Once you confirmed saved changes, you will need to restart gwadminservice.
Then check if specified SSL LDAP port became active, for instance by:
ss -tulpn | grep <port number>
You might then restart also MARS and MA agents.