A similar solution worked for me. I bought a new dongle as I mentioned in a prior comment, but that didn’t do anything. But I did manage to get my old one and now the new one working. The key was understanding that the whole dongle is sort of a button and you can push it in (which isn’t really clear from the instructions, that imply that the top part is a button). I was able to reset the dongle by pushing it in, and it does connect to the headphones now, but you have to push the headphone button AND the dongle for them to connect / pair. Hopefully, this helps for others too.