This isnt Apple error, but seems to be crucial error of Parallels with sound management via sounbdapi of MacOS. But after upgrading to MacOS 27 beta, there is serious error with Parallels desktop. And its verry annoying so i write this post as warning to others. Because there isnt rellevant beta of Parallels, i wrote to Parallels as serious bug for last updates.
After upgrading MacOS to beta, start your virtual Windows machine and connect bluetooth headphones (Apple, Bose, any vendor), sound cannot be invoked to bluetooth device. Even if you manually select in Devices and Sound submenu, even after turn off and on windows sound device, no sound goes to any BT devices.
WARNING: It may be frustrated if you hear nothing and you can manually seek what happens.
Hope Parallels fix this little but important bug for us asap.
M