Update doesn't install

Hi. I tried to update Firefox to 64.0 I let it download, i click on restart Firefox, it closes Firefox, the upgrade window pops up, the bar fills up ~half, Firefox starts. Normally the update would have to be done now. But it isn't. Firefox continued to tell me that there is an update. And when i open the "About Firefox" window its still asking me to restart Firefox to install the update. I have done this now about 20 times, it doesn't change. And rebouting my PC or deleting the update folder doesn't help either. How can i get rid of this "update Firefox now" message? (no, the Enterprise Policy Generator isn't helping either. It was for like 24h but it starts poping up again. And i'm "slightly" annoyed by it by now). Thanks