Please help is my catalytic converter done

Hi I need help, I've got the p0420 code mil is on and also as appears as pending and I scanned the car with my obd2 scanner and it seems that my primary o2 sensor is indicating that rich fuel is entering into my cat o2 sensor not fluctuating much stays at volts 720-740 , downstream o2 sensor fluctuating from 350-740 mostly stays between 640-740 slowly graph shows constant line , I'm really want to know if I need a new cat or is there something in engine that needs to be fixed first, any help I would really appreciate it

Resent replacements: DENSO 234-4122 downstream o2 sensor , and all 4 spark plugs with Denso PK20TT Platinum TT Spark Plug

Modifications: aem v2 intake , 5zigen team exhaust

Please help is my catalytic converter done