I can no longer open any door, I'm holding the card but nothing happens. Anyone care to take a look? I don't think the creator is active anymore

Just tested and it works without any problem.
Are you sure that you have read the description carefully and do everything correctly?
You must knock on the door while holding the card.

Yea I did, I've been using the plugin for some time and everything was fine. I've noticed I no longer see my hand + keycard model when I select them on the belt. Maybe that's the issue? I guess something bugged out, either my game or some other plugin is interfering. I'm going to test it today

Pretty obvious that you need to actually hold the card in hands (be able to swing the card also).
If you can't do, then with high probability some other plugin is interfering with.