I have the same problem on my 950 XL since this morning. Before I went to sleep everything was working fine, when I woke up lots of apps won't load. I don't know what build I am on since the page where the info is on won't open either. The last update was a tuesday a few weeks ago though. I'm on production preview.
The last update I had was Skype to 11.16.595.0 yesterday and today Groove to 10.17042.13912.0, Windows Camera to 2017.517.11.0 and Store to 11705.1000.78.0.
I've tried a few soft resets, but that wouldn't help. Since I read that hard reset doesn't help either I'm reluctant what to do next. What have you all done since your apps stopped working? Bought an iDroid and tossed your Lumia out of the window?
Update: I left my phone alone for a few hours and everything is working again!