apple watch

i forgot my apple watch passcode after i got it back from my friend. so i tried to reset it but it wont reset not even factory reset. i removed it from my icloud, find my, watch but still doesnt work. my friend says there is not any watch in his apple id or his device that i could ask him to erase or unpair. it seems like its not connected to any device. evertime i reset it. it starts the process and goes blank after some time and when i press the crown same old screen appears with time and charge bar. i took it to repair store but they said everytime they tried. it said error at last. what should i do. its a series 5 watch.