iwatch wont hard reset after too many pass code attempts

I've tried to reset my iwatch after I entered the passcode incorrectly, I followed the procedure below and when it went to the POWER SLIDE screen I pressed down hard and nothing happened. The power slider turned grey, but nothing happens after that.

• Connect the Apple Watch to its charging cable, connected to power.
• Whilst keeping the Apple Watch on the charger and connected to power:
  • Press and hold the side button until you see the Power Off slider.
  • Press firmly on Power Off (do not try to slide it - just press down more firmly than a normal tap), release your finger and then tap on Erase all content and settings and confirm.
• Re-pair your Apple Watch using the Watch app on your iPhone, choosing to Restore from Backup if offered the option.