Hey PiLord,
As a fellow user of the Avermedia LGP I've encountered this specific problem too.
As a first thing to note, please always add the specifications of your software, as in driver versions, obs version, whether you're using obs 32 or 64 bit, etc.
As to your problem, the Stream Engine only works on 32 bit OBS, since it's a 32 bit driver. If you're already using the 32 bit version of OBS then try to close OBS, close ANY Google Chrome processes, close Skype (Desktop version only as far as I know) then start OBS and the Stream Engine should be listed as a Video Capture Device.
Be prepared to run into more trouble, though. Avermedia's support has all but dropped for the LGP, and there's a lot of problems if you're using the newest version of Windows 10 Anniversary Update.
Keep us posted!
