Beat Powerbeats Pro - only one headphone with sound

Hello, My Powerbeats Pro only have sound coming out of one headphone. I use the headphones mainly with my Garmin watch and iphone 13 pro. The issue is on both devices. I have watched all the videos but nothing works. Also, I have been unable to do a hard reset because however long I hold the button down, and I held it for over two minutes on one occasion, it never flashes red.

The headphones have only been used about 15 times and I bought them following loads of issues with my Bose Sports headphones that dropped on one side continuously... These are not cheap and it's very annoying!

Please, please help.

Thanks