How to fix headphones that only work in one ear?

Hi so I have a set of otium Bluetooth headphones

https://www.otiumobile.com/products/otiu...

and the left headphone dose not play sound anymore, after looking online the problem seems to be a bad connection in the wire to the left ear piece. There is one panel on the right earphone that opens up but beyond that I have no clue how to fix the broken connection.