Symptoms

Symptoms may include, but not limited to the following:

• Creating a new project works, however after clicking 'Add' on the popup, the screen does not disappear (the project however is created successfully)
• Plugin update/installation does not work via UPM, even though all other settings are correct (base URL, etc)
• Project Summary Graph not showing

Cause

The cause is having an Apache caching module enabled in the reverse proxy that causes this behavior. In the case in question the module was Google's mod_pagespeed.

Resolution

Disable the problematic Apache module and restart the webserver.