This happens because we changed the "bundle identifier" shortly before release. The bundle identifier is part of the "sandbox path" where Apple saves the data in sand box protected apps.
Hence you'll now have an "old" OOTP 21 setup which you installed and ran prior to version 21.0.28 (?) and then a new folder for the newer beta builds and for the release build.
The old bundle identifier was com.ootpdevelopments.ootp21, the new bundle identifier is com.ootpdevelopments.ootp21macqlm.
To fix this and have the game find your files again, you can easily copy the "old" league folders from the old saved games folder into the new saved games folder.
First, open the OOTP 21 saved games folder via the OOTP "Game Settings" dialog -> Troubleshooting tab:
If you maximize the Finder window and scroll a bit to the right, you'll get a Finder window like this:
Click on (1) to get this same view in your Finder.
Click on the appropriate folder in (2), it should be the folder with the trailing "ootp21"
Navigate down to the saved games folder (3, 4....7)
Control-click on a league folder and then on "Copy item"
Click on the target folder in (2), it should be the folder with the trailing "ootp21macqlm"
Navigate down to the saved games folder (3, 4....7)
In the saved games folder, control-click and click on "Paste item"
Then restart and you should be good to go.
Sorry for any trouble or confusion!