I used to be a jeweler, still have the majority of my tools. Please post some pictures of the problem, I may be able to help. What’s wrong with the watch outside of the band? What material is the band made of? Do you need to recover the watch too? Do you want the band fixed so that it will come on and off the new watch?
Isopropyl Alcohol (a cleaning product) did it for me. Dip a cotton tip into the alcohol then dab along both sides of the “slot” and on the release button. Pressed the button and the strap slid straight out!!!
You might want to try WD40 spray to try to loosen the button. Overtime oils and dead skin as well as sand and salt can jam up the button. Spray both the button and aim the snorkel into the gap of the strap both top and bottom. Give it some time to do its thing and give it a try. You may need a few treatments and don’t worry about over doing it the spray won’t get into the watch and the strap can be cleaned with isopropyl alcohol.
Try cleaning it out with a warm water jet from a WaterPik or similar. Aim it in and around the release button. I have had success with my series 2 & 4 watches using this technique.
