My phone won't restart to finish the update. Why?

I am currently trying to change from Android with google applications to the open version of android, which fairphone is supporting. They call it fairphone open and it is an alternitiv open source versuon of fairephone os. So what I do is, downloading the update from this page:

https://code.fairphone.com/projects/fp-o...

Then I open it with updater and install it and finally my phone asks me to restart to compleat the update, but when I push the button it won't restart. Am I doing something wrong? Does anybody has some tips, because I really want the open version?