I think the faucet seat threading on the faucet may be stripped. Is there any DIY to fix?

Assuming you are saying the body of the faucet is stripped, not the seat itself.
Select a seat that is slightly larger in diameter, drill out the hole and rethread to fit the new seat.

Your question is a bit confusing. What exactly do you think is stripped? Older faucets have threaded stems with washers. The stems are fitted through corresponding threads in the faucet body, tightening the washer down on a seat. Newer faucets have cartridges that mostly just rotate 1/4 turn. Please clarify.

You may be trying to install wrong thread-rise seat. Make sure you have exactly the same size seat that faucet takes. No other seat will fit.

Milo