When I try open Manage Add-ons as another user, I see this message:
A long-running task has been initiated by another user. To avoid conflicts, you will not be able to update add-ons until this task has completed.
I don't think it is still installing, how do I stop the long-running task?
Update on 7/29/15: No response to this question that was posted on 7/23/15. The Support link on the Marketplace page for this add-on asked that we use Atlassian Answers for support for this plugin. The address for the plugin on Marketplace is https://marketplace.atlassian.com/plugins/pl.com.tt.staffing.timeline.staffingtimeline.