Do I need to pay network fees for cancelled/failed transactions?

Yes, you still need to pay blockchain fees because validators need to confirm the transaction on the blockchain regardless of whether it succeeds or fails.

The blockchain fee is non-refundable, as it serves as compensation for the validator who verifies the transaction on the blockchain.

On the Ethereum network, users are required to pay blockchain fees (gas fees) for computations performed during transaction execution, interactions with smart contracts, and various other activities on the blockchain.