I have tried to install a couple of 3rd party apps available in the 'Apps you can add' section of the app library - News Add-in by KEMBIT and Spotlight Announcements.
I clicked install one after the other and the initially seemed to take a long time saying they were installing so I left them over night as this had worked with another app I had installed. I realized the next day that they still had not installed and only one was showing in the standard sites content view, but was greyed out.
It said there was an error with the install, so I click the retry option - no joy. Upon navigation to the classic view I find the other app also has the same issue - I click the retry install several times on both but it just comes up saying it has had an error with the install again.
So I try clicking the delete/remove option to start afresh and it says it is unable to remove either app. I am now stuck with two apps I can neither use or get rid of. Has anyone had the same issue and found a resolution?