I am using JIRA. I already have the SAML Single Sign On add-on installed, but after installing the Jira Service Desk application the add-on stops working.
SSO redirection results in an error page and the atlassian-jira log file shows an error like the below:

java.lang.NoClassDefFoundError: com/atlassian/servicedesk/api/organization/OrganizationService at com.resolution.atlasplugins.samlsso.jira.servicedesk.OrganizationAssignerWrapper.create( [?:?] at com.resolution.atlasplugins.samlsso.jira.servicedesk.OrganizationAssignerWrapper.get( [?:?] at com.resolution.atlasplugins.samlsso.jira.userauth.JiraUserPreparator.doPrepareUser( [?:?] at com.resolution.atlasplugins.samlsso.userauth.AbstractUserPreparator.prepareUser( [?:?] at com.resolution.atlasplugins.samlsso.userauth.PrincipalProviderImpl.providePrincipal( [?:?] at com.resolution.atlasplugins.samlsso.userauth.AbstractLoginHandler.login( [?:?] 


There are two possible solutions to this:

Solution 1

If the "Atlassian Universal Plugin Manager Plugin" is not up to date in your Jira instance, upgrading it to the newest version will make the add-on work again.

Solution 2

If solution 1 doesn't apply to your instance, you need to uninstall the add-on and install it again.
Although the existing add-on configuration isn't deleted when uninstalling, it's recommended to back it up, should you be able to.
You can do that via the System & Support section in the add-on configuration:

You can now uninstall the add-on and install it again. This will fix the problem.

You will now also have access to Jira Service Desk specific settings, which will become visible, if "Enable User Update" is activated.
These will provide more control over actions related to Jira Service Desk organizations.

You can read more about it here: