Help

I've just bought a second hand Google pixel 2 watch and it won't connect to my phone at all, it keeps asking for the old pin...which I obviously don't have. I've rebooted it go knows how many times over the last four or five hours and nothing is working. Any help would be greatly appreciated

I've just bought a second hand Google pixel 2 watch and it won't connect to my phone at all, it keeps asking for the old pin...which I obviously don't have. I've rebooted it go knows how many times over the last four or five hours and nothing is working. Any help would be greatly appreciated