The reason why this is happening is because the newer version of the software doesn't support the old one. Don't try to open the folders or the content directly. Use another approach like Import. Start KennelSuite IX then go to File > Import or look for this option in the main menu and use that instead to open the folder. It might or might not work.
If it doesn't work, then compatibility is the problem here. You should know that not all apps support opening previous files.