Power issues inc after a new battery

My daughters Beats Solo have all of a sudden developed a fault.

They work spot on using 3.5mm (wired) but when it comes to the wireless side, we struggle to even get them to power on.

Initial did the "reset" options for these headphones, so the power and down vol as well as the connect to charger and hold power for 20sec which most posts suggest.

Opened them up to replace the battery, as I know its another known issue, as I has a spare as was due to replace battery for my own Solo3. Before I did, I decided to pull and reconnect the battery. They would power up and could connect to them wirelessly (my iPhone wasn't connected originally but would show up, connect then they would go off), would flash up with ~70% battery.

Changed the battery and got the same, powered up, connected and died.

The power button appears to be unresponsive as well.

Any recommendations on what to follow up with trying to resolve next