This morning the security's certificate for FME Server Javascript Api v3 seems to be invalid :
https://api.fmeserver.com/js/v3/FMEServer.js
That cause a lots of problems over here, all our FME Server web apps our down!
We had to switch urgently some apps in http. It's working but the interface is a little bit different.
Maybe in the future we'll consider hosting our self the Javascript file.