It looks like it's a known issue that SteamVR games launched from the itch app can't find the headset because of sandboxing. To launch after installing with the itch app, right click and choose "Open folder in explorer." From there if you go into the "Packing Up" folder and double click Packing Up.exe it should be able to find your headset.

Hopefully it's alright for me to post here. I played your game on my YouTube channel and gave some feedback and some props on your game here. We're a smaller channel however we've growing fairly quickly and this was my first ever time trying VR on the channel and your game happened to be uploaded around the time I was making this video. I'd welcome you to come check out the video and the video containing your game will be up tomorrow the 13th at 9AM. Have a great day and keep making games because this was very cool! https://www.youtube.com/channel/UCXoSYqva_jP83Ah3YOZx8eQ