Audio not playing notes above the C on euphonium

When using Muse Sounds tuba, I noticed that nothing is being played above the C (1 ledger line above the staff). Was it made to be like that or is there an issue with muse sounds? The euphonium is required to play a lot of notes above that C so there being no audio is really inconvenient. I don't really want to resort to switching to a trombone or french horn sound so at the moment, I'm stuck with using MS Basics.

Although a bit laggy and crackly at times, M4 has been great! I'm looking forward to improvements in the future :)