You definitely didn't need to buy a second license, so I processed a return for your second order yesterday. Supposing the 'Check for Update' option didn't bring up the latest version thereby causing confusion, it's likely because you were even on a version that was older than anything to have been released in the past few years. Using that old of a version would also explain why your data didn't show up automatically in the new version—old versions kept things in a different default save location than recent ones and the update looks in the more recent save location. Refer to the instructions covered here to access your data file from before, which you can rest assured is definitely safely stowed on your Mac still (the update process even backs it up for you):
viewtopic.php?f=3&t=4603For your situation, you're likely going to skip over the various locations in step 4 and 5 to use this path: ~/Library/Application Support/CheckBook 2
Good luck and keep us posted!