In general:
1) See the plugin page of that plugin, and search for potential FAQ, etc.
2) on that page, click on the autogenerated "issues" link on the right, and search in the issue tracker for potentially matching issue
3) if not, then you're on your own: do a thread dump and try finding what Jenkins is doing when it's stuck
3.1) the Support Core Plugin might be useful to generate a dump you may want to associate to new issue you'd file
3.2) as we're talking about OSS plugins where people work on their free time, there's IMO a non negligible chance your issue will NOT be fixed soon if you don't consider proposing an associated PR
HTH