Since yesterday, my phone started throwing a Failed(405) error when trying to register to a FusionPBX server. I have tried resetting to factory settings and reinstalling the FusionPBX server on multiple OS's several times, but unfortunately, without any luck. It did work before, but after a few hours it randomly started throwing this error on every FusionPBX installation I've made.
I have tried the solution provided in this answer already, but unfortunately without any luck. I'm running FusionPBX 3.8.4 on Debian 8.