Series 3 watch restarting

I was gifted my moms apple watch and I removed the watch from her accounts and hard reset it so i can pair it to my phone. The watch had not been used for a while and is currently on watchOS 6.3 and when I am prompted to update the watch, in order to continue the setup process, to watchOS 8.7. 1 the watch itself starts to continuously reboot. I don't know if this affects the set up process but once I finally finish downloading the update, it displays that it is preparing the update and has been stuck on preparing for a couple days. I've restarted both phone and watch, my phone is updated, and I've unpaired and re paired over and over again. If anyone knows a tip to help that'd be great, thank you.