So, I was configuring our on premises dev and QA SharePoint 2013 to support apps as well as connect to ACS, using this amazing post on MSDN:
Second time doing it, only took me about 30 minutes to complete the process, as I simplified it a bit by having all the power shell commands and scripts ready to paste.
But, in both times, when I thought I was done and ready to go, I got this annoying error message when ever I tried to add an app to my site:
"Sorry, something went wrong with adding the app. Click to retry."
Now, first thing I tried was an IIS Reset, since I was messing around with some certificates and was positive that would be it.
That didn't work. The thing it, it took me both times about 10 minutes to figure out that it was the SPTimer service (OWSTIMER.EXE) that needed to be restarted!
Now, I didn't notice it anywhere in the instructions so I thought it was worth posting.
Actually, when ever you change some major configuration in your SharePoint, it is very smart not to forget to restart the SPTimer service.
So, after doing that and just clicking "retry", all is good and the app is working on premises as expected:
Hope this helps someone out there getting the same error... if you are sure you did everything right in the configuration - you might actually be correct! Just remember to restart services for them to pick up your changes...
Did you notice this error in other situations? Post in your comments and I'll update my post.