You must get one of these 4 cases:
Case 1. Heads first, heads second.
Case 2. Heads first, tails second.
Case 3. Tails first, heads second.
Case 4. Tails first, tails second.
The first 3 cases are cases when there was at least 1 head.
Only case 4 contains no heads.
The probability is 3 ways out of 4, or
Edwin