I don't usually comment on typos, but I expect you mean using rather than suing on your Mac.

Hope you get your problem solved soon. That it happens in multiple files is a real puzzle.

Remember you can send an offending file to Finale Support via the "Submit a request" link at the top of this page.

Middle C (like other notes) can be set as a MIDI controller instead of a note. You will need to check the settings in your MIDI controller. That should be where the problem lies.

https://usermanuals.finalemusic.com/FinaleMac/Content/Finale/MIDI.htm?Highlight=midi%20controller%20note 

Only the middle C's during a repeating pattern don't play both in harp 1 and harp 2 (it's a harp duet). If I start a new document, select piano and play a G major scale as suggested, the middle C works fine during playback. I did find a way to make the missing middle C's sound during playback by deleting them and re-entering them. Tedious workaround, but it solves the issue.

Only the middle C's during a repeating pattern don't play both in harp 1 and harp 2 (it's a harp duet).

Ahhhh... this is not uncommon with harp VIs but I've seen it with piano, too. This can happen when a note is still playing back when the next one is supposed to start. There are a few ways to address this but, without more information, I will not know which one to suggest.

https://makemusic.zendesk.com/hc/en-us/community/posts/215729367-General-Discussion-House-Rules 

I only run into this with imported MIDI files, never ones that I create. When it occurs, I drop the file into a DAW, open the piano roll, Select All and, holding the Control key, drag the right edge of one note slightly to the right. This shortens the length of every note slightly avoiding the overlap. I then export the MIDI or MusicXML back into Finale.

Laurie,

First, I must tell you I know nothing about writing music for harp. I play bass trombone in the Olathe Community Orchestra, and I know there is one on the far side of the orchestra but that’s it.

It looks odd to me to see measures without proper note or rests for the time sig. However, my thoughts are Finale made some notes rests. Turning playback off. Perhaps it is a harp bug in the software I don’t know. I would really doubt Mike H cause since there are no long notes before the offending middle C.

But using the JW Change plug-in and turning “playback” on, all the notes play. I see you don’t have Finale 27.3, so you didn’t get JW Change already installed. Here is the link to get it if you don’t have it already.

https://www.finaletips.nu/index.php/download/category/43-64-bit-windows-plug-ins

 You can just unzip it and put it into your Finale/Plugins folder. There is a Summer sale going on right now and you can upgrade for $79 bucks. I would urge you to take advantage of it before it ends. It includes several of the JW plugins updated to 27.3 included. I use JW Change and JW Polyphony all the time.

I added the reply here since I got errors on your email address. I don't know if they went through or not.

Some of the middle C notes don't sound ....

Are you saying all other notes play as normal? Plus even some middle C on other instrument s play as normal? If you start a new document and select piano and play a G major scale does middle C play?

Laurie,

would you like for me to look over your file and see if I can find any  issues with it? Let me see the original not an edited where you got it to work.

My email is e e biggs1 at gmail dot com but no space and using normal email verbiage. Keeps out the spammers.