Write a variable tag with control client

Does the user that you are login into have a password?  I know in version 2020 forward passwords are required for security, so if one logs onto a system without a password, communications are cut off.

Check the syslog or trace log in .\Logs folder on your client machine where you may find out the cause.

It is not possible to create a user and replicated this user across the entire system at runtime. So, all users or/and roles need to be created at design time and you should distribute the compiled projects to all nodes of your system (via Run/Copy or Backup/Restore as the deployment feature is unavailable in this version). Any discrepancy in the projects between the nodes at runtime will cause unpredictable problems. Thus, the login user must also exist on the remote servers. 

It is worth trying to create a new user on your engineering machine. Then restore the compile the projects on both server and client sides. Hope this would be helpful in resolving your issue.

Yes the user does have a password. I didn't assigned any roles though.
But I did the exact same thing on a server and it worked fine, the login() function doesn't crash the com (except in this case I'm using a licence server and "Server and Control Client" role in the Computer Setup Wizard).