MY HOA HAS ISSUED A VIOLATION NOTICE AND HAS STATED IF I DO NOT COMPLY WITHIN A CERTAIN TIME THAT THEY WILL DEACTIVATE MY GATE PASS TO THE PROPERTY. CAN THEY DENY MY ACCESS TO MY PROPERTY?

It's legal. You agreed to it. Comply or move out.

I have a HOA too and I am trying to move myself, I don't like them, they are nosey, expensive and largely useless but if you agreed to it, it's legal.

Why do people REFUSE to read the terms and conditions of their HOA before signing their lives over to them?

Check your contract. You just may find that you allowed them to do just that.

Only if you signed a contract or a legal document that says that you agree to those terms.

Even if it says so in the contract, that doesn't make it legal. Sometimes if a clause in a contract is just too outrageous, the courts will say it's "unconscionable" and then it doesn't count.

Is this "gate pass" the only way to get in? There must be a human who's responsible for the gate. If your gate pass is deactivated, you still might be able to get in by telling the responsible human to let you in -- what I'm getting at here is that maybe the contract says they can deactivate your gate pass but doesn't say they can keep you out of the property -- see, if there's more than one method of getting into the property then they have only excluded one method, but you can still get in by another method.

You may need to go to court and get an injunction to stop them from deactivating the gate pass.

The HOA CANNOT prevent you from accessing your property without a court order. This can be considered an illegal eviction.