Thunderbolt display audio issue

I have two Thunderbolt displays connected to a MacBook Pro 15 inch mid 2014. macOS Big Sur. I can only get audio from one display unit at each given time. Previously I got audio from both units simultaneously, for instance when listening to music. Both screens are connected using apple cables. I have tried audio settings, i.e. changed and even tried Elements organizer but nothing seem to resolve the issue. Any advice/help would be appreciated, thanks.