I'm no tomcat or java expert, but the line 'no output folder' suggests the the account running the FME Server Services might not have sufficient read/write access to the install location and share resources location

Thanks @hkingsbury​ 

Actually it was just one of two mistakes, or rather forgotten steps.

I have done this exercise before, and did document the necessary steps at the time, but that documentation apparently has been lost (can't find it), so I'm retracing my steps.

The two steps I forgot was:

1. Adding the AD account to the local Administrators group - which your suggestion pointed at
2. Deleting all engine logs from the old account (C:\\ProgramData\\Safe Software\\FME Server\\resources\\logs\\engine)

When both steps was taken care of, the web interface started as expected.

So again, thanks for pointing me in the right direction 🙂

Cheers.