Yes, it is possible for a miner to verify transactions and end up earning nothing. There are two criteria for a miner to  be qualified to earn Bitcoins: - Firstly, you have to verify a transaction worth 1 MB. - Secondly, you have to be the first miner to get the correct solution to the PoW equation and thus add the new block. If a miner fails to meet these criteria, he loses out even after spending resources to verify a transaction.