Apple Watch series 5, 44 mm
I forgot my old Apple ID, so I need to reset the watch to merge them with new Apple ID.
User profile for user:
Community User
You can ask apple to remove the activation lock online on this page;
Online Activation Lock Removal Tool.
Or this;
If you can't remember/gain access to the apple id that paired the watch to the phone.Take the watch and it's receipt along with some photo id and any other proof of ownership to an Apple Store and request that they remove the Activation Lock for you.