4.19.1 or 4.20.x breaks Jira/Service Management and I cannot upgrade passed 4.18.1

[Warren Gunn]

I need help with upgrading as it breaks service management module and I cannot access any tickets or queues once I upgrade to either of the above versions. It seems to upgrade fine and everything comes up but then I cannot access the service desk.

[M Amine]

Do you have any errors in the logs? can you share any error message? 

When you go into "Administration" (Cog Icon) > "Application", do you still see "Jira Service Management" ? and see the number of licences consumed? 

Are you in one of the groups allowed to use JSM?