P0420 replaced O2 bank 1 came back on now what?

Maybe try switching your 02 sensors with each other and take it for a test drive and see if it’s still running the some code.

I had this issue when I put in my long tube headers the 02 sensor welded it’s self to the header and I had to rethread it and figured well that was weird only after a day of driving it. Then switched it to the other side and I got a different code and sure enough it welded itself to that side as well. So went down to parts store bought a quality new one and issue was gone.

Now I know you said you just replaced one but maybe check it again. You could possibly have bought a faulty one/low quality. Or the heat cycles from the exhaust could have caused it to come loose to if it wasn’t tightened enough. Or retightened after the first few heat cycles