The Mac JamKazam app was updated today. It's Build 1.20 - "1.0.3680". To see the app version, select the JamKazam --> About JamKazam menu item. 

(From the official post here)

JamKazam has recently seen a large number of new users.  We are working on a number of issues.   
May 22nd, 2020 (Take 2)

The May 19th client release is back out w/ the JamTracks bug fixed.

Additional changes:

'TURBO' mode added, and is now the default.  This mode should result in better audio quality.

May 22nd, 2020 
We had to roll back the May 19th release because of a bug introduced related to playing JamTracks.  We'll get that fixed and re-release.