Good morning
I found the problem
it seems that if an .ogg sound file is poorly compressed or incorrect, it creates a bug in DCS
it becomes completely impossible to add sound files to any mission, a sort of internal link to the simulator with the directory in question where this file is located, prevents any use of sound files thereafter.
the solution is as follows, you must completely delete the files in question from the directory where they are located, immediately when you restart DCS, everything works again.
I think we seriously have to say that this is still a DCS bug and this shouldn't happen.
I hope I can help other people by fixing this problem.
simracingone's post in Sound selector no longer works was marked as the answer