Watch band stuck

Here's a detailed article covering those various bands and how to remove them.

Change your Apple Watch band - Apple Support

Holding down the release button properly and then sliding usually does the trick.

try

Apple Watch band release button stuck - Apple Community

and

I am unable to remove my watch band - Apple Community

I have that problem sometimes. I have a case little case on mine protecting the face & sides & sometimes that makes it more difficult.

You may have tried this already, butt thought I'd tell you what helps me.

If you have a case on it, make sure you pull it down underneath the button that removes the band. This sometimes makes it a little harder to press the release button properly, but it still helps. Also, simply getting the button in the correct (sometimes a little hard) position is key.

Another thing, if you have dry skin, have been working &/or sweating, or doing anything to do with dirt, this can cause the to "stick" as well as the watch bands.

Simply take a moistened paper towel/cloth/baby wipe, etc & wipe everything off. Sometimes a q-tip may be needed. I've found this helps to get the debris out & makes it easier to remove the band.

Again, you may have tried some of these already, but I hope it helps.