I've been struggling with this since yesterday and still have no idea how to solve this.
It all started with a simple Plugin-manager update. After that Jira stopped working.
Restarted Jira- got an error that 2 plugins failed to start, the Global Issue Navigator and the Quick Edit plugin.
I've managed to load Jira by disabling these 2 plugins, but you can't really do much without them.
So after playing around for more than a day, including upgrading Jira to the latest 8.7.1 and Java to 1.8.0-241, Jira looks like it's loading, but then I get an error page with the following details:
java.lang.NoClassDefFoundError: com/atlassian/jira/ComponentManager
java.lang.NoClassDefFoundError: com/atlassian/jira/ComponentManager
at com.intenso.jira.contentinjection.filter.ContentInjectionFilter.getContentInjectionRegistry(ContentInjectionFilter.java:29) [?:?]
at com.intenso.jira.contentinjection.filter.ContentInjectionFilter.doFilter(ContentInjectionFilter.java:42) [?:?]
..........
