Am I the only one who can't hear certain instruments?

[Red_Room]

So, I played a small original piece I made (called carousel) that mainly used the organ and music box instruments. However, when I played the sequence, it made no sound. Recently, I made a small practice sequence using a grand piano and it worked perfectly well, but when I tried adding a violin, it didn't play sound. It seems like the only instruments that work are from the first category. Why is this?

Edit: I made a new sequence that used synth instruments and it worked fine, so it only works for certain ones

[Plasmatier]

I have a similar issue, its been like this for a while and I don't understand why. Multiple older pieces of mine are now unplayable because significant portions are in instruments that refuse to load.