Apple watch keeps showing enter passcode

I tried to find the solution for the problem of my apple watch but couldn’t solve it. After updating new watchOS, my watch can’t automatically unlock when on my wrist, I try to type the passcode but it stays unlocked. Then I erase all settings and contents of the watch but it still stays unlocked. Finally I unpair the watch from my phone and try to repair it but it keeps showing enter passcode. I try to hard preset the watch, as well as other solutions for similar problems but it always stays unlocked. I hope someone can help me. Thank you very much.