What version of Tableau Server is in use? TSM would be the command for a version 2018.3 or later but the example above shows a mix of TSM and Tabcmd so I wasn't sure which is in use.
As for the user login - be sure that the user is a member of the site with correct rights.
here are some more details to assist - Troubleshoot Server Sign in Problems - Tableau
I hope this helps and please mark this post correct if it resolves your question.
Please check out the following article that has some solutions to the behavior that you are experiencing.
Patrick is right, TSM replaced TabCMD, but it was released in 2018.2, not 2018.3.
More information on the upgrade to TSM can be found in here: Upgrade from Tableau Server 2018.1 or earlier to Tableau Server with TSM - Tableau
Hope this helps!