I think the activation lock or watch lock causes this issue.
Following steps worked for me:
Reset apple watch with erase all content
Pair watch with a different phone it will ask to remove the activation lock and it will require your appleid and credentials
After the sign-in just cancel the pair process
Pair with your original phone
Optionally u can try the icloud.com/find and from the all device menu just remove your watch
I havent tried but if my theory is ok it should help also.
regards,
Rob