I sent someone bitcoin through cash app and it says confirmed but the recipient said they never received it, is there a reason this could be happening? Or is there a way for me to get it back from the block chain?
There is no way to actually get it back. You can always check if they really received it by going to blockchain explorer and track the transaction here:
Sometimes the transaction might not show up on the receivers transaction tab but adds up to their wallet. Via the link you can paste their wallet and check by yourself if you sent it to the correct address. If it says confirmed they have received it for sure.
If this doesn't help you can directly contact the app support.