After endless emails and being fobbed off with discount codes from Turtlebeach who kept telling me to buy new ones I’ve found the answer posted on the Microsoft answers page. Looks like it’s a Microsoft Xbox issue….
“Known issue: Some third party headset adapters are unable to adjust game/chat audio mix when playing with the new Xbox Wireless Controller (the controller that comes with the Xbox Series X|S).
Workaround: There is no known workaround at this time but we're aware and looking in to the issue. If you connect the headset directly into the 3.5mm headset jack of your new Xbox Wireless Controller, you can adjust game/chat audio via the Xbox Audio Mixer settings by going to Guide > Audio. If you still wish to use your headset adapter for quick audio adjustments, you can use a previous generation controller.”
Here is the link:
Hope this helps you all! Just sit tight for a Microsoft fix!