UI Builder: Can't access Unified Navigation App for modification

[Eric87]

I've been modifying the default landing page within Unified Navigation App (I created a variant), I was resizing some elements and impersonated another user to see what the variant looked like in-browser.

When I ended impersonation I went back into the UI Builder interface and opened the application I receive the following error message stating that the application cannot be found.

I went to sys_ux_app_config and can see the application configuration record. If I open the record, there is a button that says "Open in UI Builder", though this results in the same error.

I've tried using different users as well as different browsers (Edge & Chrome). 
Has anyone encountered this issue? This is on the San Diego release.

[Eric87 · Accepted solution]

Fixed this by clearing the cache.
Simply going to cache.do did the trick.