One instrument/player does not appear in cue list

Any reason why one particular instrument might not show up in the dropdown list when adding a cue with Shift-U? I have three trumpets in the score, plus an addition trumpet renamed “solo trumpet (B-flat)”. The solo trumpet is not available to cue. I am trying to cue on another trumpet staff. Thanks.

Normally the only reason an instrument wouldn’t appear in the list of instruments for a cue would be if you were trying to cue to itself. If you can’t get to the bottom of it, please feel free to post the project here and we’ll take a look.