Unable to reset apple watch series 2

I have an old apple watch series 2. it was paired to my iphone which since was reset to factory defaults. so meaning i dont have a record of this apple watch being paired to it, and i dont have saved back up of that phone. i have removed icloud lock , so this watch do not come up under my device list in icloud account. when i check the watch serial number in imei check tool it says that Find My device is off, so i m good there. So the watch still boot up as they are paired to the phone. Things i tried: press and hold Power slide button while watch are on charger , that doesn't bring up Reset to Factory pop up. Please help if anyone is aware of a fix or possible steps to take. Thanks in advance