Having the same problem with the Mac version 27. 

Still in communication with MM, but still no resolution. It seems that JABB failed to install the latest Aria Player and Engine, though I downloaded JABB and reinstalled it directly after installing WinFin27. However, having updated both (no thanks to MM, I stumbled to the latest versions while searching MM site - it wasn't easy), Aria fails to recognize my installed JABB files. It's a "slot 0" error, whatever that means. I was told it meant Aria Engine was out of date, but I still get the error after updating.

In case this might help someone else, go to Settings in the VST Viewer (by way of MIDI/Audio|VST Banks and Effects|click on the pencil). There are 2 buttons there to update Aria Player and Aria Engine. 

I find this website a mess. It's not easy to find what's needed, and the instructions and versions are out of date.

I'm on a Mac and have been at this for almost three weeks, ever since I downloaded v.27 and JABB 3. I cannot find a solution. I have reinstalled Aria, Finale v.27, and JABB. No good. I can get JABB to play but it always crashes within 30 seconds or so. Also, JABB won't load the first time I try playback. I must first play the piece through midi then switch back to Audio Units in order to get JABB to load/play. I've had a ticket in at MM since day 1. MM replies every 3rd or 4th day with pretty obvious stuff (change a setting here and there, restart the computer, uninstall, reinstall, make sure the right device is selected, etc., etc.). Has anyone out there figured this out? Thanks

Stephen,
I received this from Chad at makemusic the other day:

Thanks for contacting us.

We are currently working to update the Garritan installers so that they will automatically configured themselves with Finale v27. That work is still ongoing at the moment, so in the meantime, you can manually configure your library with Finale v27 by following these steps:

Exit Finale and leave the program closed during the remainder of this setup process.
Follow these links to update your ARIA Player and configure the ARIA Player with Finale or PrintMusic.
Restart your computer.
Click here to download the file "JABB3.zip".
Unzip JABB3.zip and open the JABB3 folder.
Drag the following files from the JABB3 folder to your desktop:

JABB Drum Sets and Percussion.xml

GarritanJazz3.soundmap

Finale (Version 27) does not require the file GarritanJazzinstrument3.txt.

Press SHIFT+COMMAND+G to open the Go to Folder dialog box.
Type "/Library/Application Support/MakeMusic/Finale 27"(without quotes) and click Go.
Drag JABB Drum Sets and Percussion.xml from the desktop into the MIDI Device Annotation folder.
Drag GarritanJazz3.soundmap from the desktop into the Data folder.
Relaunch Finale.
Garritan JABB3 is now available in the Device column of the Score Manager, as well the Sound Map Priority dialog box.

Please let me know if you have any follow-up questions about this!

Best,
Chad Mathis | Manager, Customer Support

Also this as a follow up:
Hi Bill,
Thanks for the update. I'm glad you wrote back, because I have another update for you.

Over the past few days, our team has completed the work of updating the Garritan installers, so you have a second option for resolving this.

The first option my email from Monday is still perfectly valid, it simply involves downloading and manually placing a couple of files into, so if you comfortable navigating the folders on your C: drive, that is still a quick fix.

However, if you're not comfortable completing that process manually, then you may also redownload the installer for JABB3 from your MakeMusic account and reinstall JABB3. This will automatically configure JABB3 with Finale v27
https://account.makemusic.com/

This second option will take a little more time because you'll need to reinstall, but the configuration will be completed automatically.

Regardless of which method you choose, just please make that both Finale and the ARIA Player are closed during the process, and restart when you're done.

Please let me know if you have any follow-up questions about this, and safe travels!

Good luck

Thank you Bill. I think this was one of the first "fixes" MM offered me. It did indeed make JABB appear in the device column of the score manager. Still, I must first switch to midi then back to audio units for JABB to load. This is followed soon after by a crash. I'm going to try it again and I'll let you know. Did you actually get this to work?

Just saw your second post. I'll give it a whirl.

Bill, 

 It did not work. Exactly the same issues. Thanks for the help anyway. But it worked for you?

SW

MakeMusic should update all help topics to cover Finale 27. Don't roll out any software that isn't fully tested. Usually, guinea pigs are paid as test subjects. In this case, users have paid to become guinea pigs for MakeMusic. At the moment, Finale seems to recognize JABB in Score Manager and VST Viewer, but brings up a "slot error" when it tries to load sounds. My 3 week correspondence with a MakeMusic tech has proved to be ineffective, after multiple uninstalls/reinstalls, and even creating a new Windows account (an extremely tedious process). I still have no sound from either Fin27 or Fin26. I'll test the "new" JABB install and report to this forum. 

Windows 10 Finale 27

FAIL. Still getting slot errors and no sound after re-installing. One thing I've noticed is that the slot error shows a ridiculously long path to the instrument file, as if Garritan appended each subsequent install to the previous install. So,I've uninstalled Fin27 and all recent Garritan and Aria installs.  I left the old Garritan and Aria files intact, thinking they are connected to Fin26. My fingers are crossed, all but one.

Mixed success. Reinstalled Fin27, and JABB after uninstalling same. Played an older file just fine. Created a new file with Wizard. Wouldn't play - said I had an outdated Aria version.

Just closed and repopened Finale, Reassigned Playback Sounds, and it worked. So at this point, I have success. I now need to check if I have a working Fin26.

Dare I try updating Aria? This install loaded 1.872; the new version is 1.959.

Success! Updating Aria Player to 1.959 worked, and I have JABB playback in both Fin26 and Fin27. Also, I discovered an undocumented bug fix. In Finale Jazz font, the dot on the dotted-eighth rest is spaced properly. Small issue: starting playback using click-spacebar still causes the cursor to freeze. Fast fix: start playback from the Playback Controls, then click-spacebar works with the moving cursor.

I'm hesitant to install the updated Aria Engine (from 1.959 to 1.967), as the Engine version supposedly match the Player version. I'm going to leave well enough alone for the time being, until I'm ready to possibly uninstall and re-install everything again. "Not today." Aria-Arya joke.

Stephen - Sorry for the delayed reply... Yes, I manually configured the library as they recommended and it worked for me on both my iMac and MacBook Pro.