OBS and NVENC error

Hello! I have just installed OBS studio (complete noob when it comes to screen recording) and I am trying to record my screen & audio. When I try to do so, I get this error message:

Context: I have a laptop with an Nvidia GPU and I use NixOS unstable on it. My system configuration (in use at the time of writing) can be found here.
I have just checked my Nvidia driver version and it’s fairly up to date (550.67). For now, I suspect that I might have made a mistake while installing the Nvidia drivers.

Please help me determine if this is a NixOS config mistake on my part or I am misusing OBS (in which case I will turn my attention to the OBS help forums). Thank you!