No problem!
Thanks for that clarification. Did you purchase MSFS using steam or the MS-Store. I don’t see why that should make any difference, but I purchased via the store, & if you purchased using steam, then any suggestions or advice I give may not valid.
On my PC, in Options / General Options / Sound, if I set the “Main Device Output Selection” to my monitor’s speakers (connected via an HDMI cable) and the music slider to 100%, I can hear the UI music thru the monitors speakers.
Can you hear the music as well if you do the same?
If not, that suggests a problem is in either the Windows settings or NVidia HDMI sound settings (if such settings exist - I don’t have an NVidia GPU, so cannot determine that). Have you updated your Nvidia drivers recently - i.e. is the driver version different from the one used before you reinstalled Windows 11 - Just guessing here, to be honest.
Also, see if the solution in this thread works for you