When I try to enter a # to name a note instrument like Strings C#3, BBMO ignores the # and I just get C3. If I import something already named with a # its accepted, but I can’t enter a new #. It’s not my keyboard, and this has happened over several days. I use the enharmonic flat name instead, e.g., Db, but that’s not ideal.
I can verify what you’re reporting in Vivaldi. The only key that works in the shifted numeric row seems to be the ampersand (&).
Thanks for reporting this! I’ve forwarded the issue to the dev team. As a workaround, you can copy (Cmd+C or Ctrl+C) the # and paste it (Cmd+V or Ctrl+V).