Transcoding not working with PMS on Unraid

I have installed PMS on Unraid and things have been working flawless using directplay. I am now looking into using the Plex apps, which requires me to use the transcoding function (no directplay available on IOS and TVOS apps).

I hoped this may work out of the office, but it seems not. I am getting the same error with the Plex APP for IOS and TVOS, so I’d assume it’s a server issue?

Error on IOS app: Playback was terminated by the server. Conversion failed. The transcoder exited due to an error

Same error message with TVOS app.

Checked the log in the PMS container:
Critical: libusb_init failed
[s6-finish] sending all processes the KILL signal and exiting.

Any thoughts?