Where is the band release button on the Apple Watch?

If you already tried (to no avail) all the steps provided in the support article that led you here, I suggest that you visit an Apple Store, Authorized Reseller, or Authorized Service Provider among this list:--> https://locate.apple.com/choose-country-region

Regards

Giulio

Check if this helps -> Change your Apple Watch band

Change your Apple Watch band - Apple Support