As some have noted those gates are pretty notoriously nonfunctional. I accidentally ended up not paying for parking during my 4 night stay -- on entry I didn't go to the front desk first, just hit the speaker/help button, and they let me in without issuing any sort of ticket or receipt. I parked, asked about it at the front desk, they said I'd pay when I left.
A few days later, left -- realized I still had no receipt and the room card did jack. Hit the speaker/help button again, and they waved me through without a word. Checked my credit card statement - no charge.
Don't recommend doing this, as it was an honest mistake, and your milage may vary. But those gates are pretty inconsistent.