Apple Watch Activation Lock
I don't have proof of purchase for my apple watch to remove the activation lock. What else can I do?
Apple Watch
This support article has information about Activation Lock on your Apple Watch and how to turn it off. --> About Activation Lock on your Apple Watch - Apple Support
If you cannot prove to Apple that it is yours as part of an activation lock removal request, then you will absolutely need the account information that was used to set the lock.