Recently I ran into this error when users tried to log on to a second partition.
A user session on the server could not be created. Try to start the client again. If the problem continues, contact the Microsoft Dynamics Ax administrator.
It’s weird, because I had just added users with the Active Directory Import Wizard. They already had access to the initial partition and I had no trouble accessing the second partition with my own account. Because of that, none of the solutions I found online worked: the transaction log wasn’t full, the CREATEUSERSESSIONS stored procedure wasn’t broken and the config file was correct.
After comparing records in the UserInfo table I noticed that the new records had no values in the fields Language and HelpLanguage. They are, however, mandatory fields in Ax. They’re also used in CREATEUSERSESSIONS. After setting a value in both fields the problem disappeared. And so peace and productivity returned to the office and everyone was happy.
Well, I wasn’t happy. How is it possible that mandatory fields don’t have any values? I used a standard Ax tool to add the users to the system. After digging through the code it turns out (hooray for cross-references) that a bunch of values for the UserInfo record are copied from user Admin. Sure enough, there was no Language or HelpLanguage defined on that record. For some unknown reason, those values were gone and caused invalid UserInfo records to be created.
I fixed the data for user Admin and never had that problem again. Now I was happy too.