phone won't connect to pc

(My phone is a j7 perx, sm-j727p. They didnt have the option, so i picked the closest one.)

My phone says custom binary blocked by frp lock. Would love to be able to flash ot with stock firmware, but it only connects to computer when in download mode, and when it is connected, the pc says unknown USB device(descriptor request failed) driver error. Pc works fine with all other phones. How do I get it to connect?