Some of Mac users cannot upgrade to the latest version. The problem affect both Pro and Free edition. We are aware of the issue and is working on the fix.
At this moment, we are building and testing the Mac installation image for the latest version 1.9.6 for Pro and Free edition. We will make them available as soon as ready.
One workaround is to downgrade to the 1.8.1 and then upgrade.
JoyBidder eBay Auction Sniper Pro 1.8.1 for Mac
JoyBidder eBay Auction Sniper Free 1.8.1 for Mac
Sorry for the trouble, but please make sure to upgrade to 1.9.6 as soon as you can.