This is not so much an issue as a solution that I figured out and wanted to share. I was having problems using the button controls on my bluetooth headphones in that I couldn't get the pause/next/previous buttons to work even though the Poweramp bluetooth settings were correct. It turns out that as my headphones has built in Voice Assist (Google Assistant, Alexa, Siri, etc), this would override the music controls as they use the same button. Turning off Voice Assist in the headphone app fixed the issue.
My headphones are Sony WH-CH720N's, but I suspect this will work for many other models and brands.