Igpu - internal Graphics. If you have an Intel Cpu you likely have onboard graphics.
PiMax is a steam compatible headset. The headset more or less is seen as a Vive headset for comparability.
The headset is fully compatible with steamvr. You must have a software and/or hardware conflict.
Have you tried installing tge Nvidia driver support mentioned?
Might be best to setup with support a Teamview session.
Di you have a vive or rift? If not then the problem you have would likely affect them.
Please post your system specs.
Graphics Card & driver version