Add-ons are not available after upgrading Universal Plugin Manager (UPM) in Confluence Data Center
Platform Notice: Server and Data Center Only - This article only applies to Atlassian products on the server and data center platforms.
No add-ons are available after upgrading the Universal Plugin Manager in Confluence Data Center, and the add-ons menu does not appear. UPM itself is also not available.
The Universal Plugin Manager plugin is not completley cluster safe, and requires a rolling restart to propagate changes to each node.
After Updating the Universal Plugin Manager, you should restart each Confluence node in turn (rolling restart) to ensure the change is propagated to every node in the cluster.