Can't confirm the payment?

Hello,
I buyed BTC and payed the money and confirmed the payment.
After 2 days the seller send me a small payment back to tell me, (over the payment reason) that he got the money but can’t give me the BTC, because I need to authorize the payment.
But I already did it.
What I should do? (I don’t want to lose the sec deposit)

Open a dispute (cmd+o or ctrl+o). You will not lose the sec. deposit if all was correct. Only clear violations of the trade protocol leads to loss of the security deposit.

Thanks
Just want to say that I confirmed the payment. Probably a bug.