Next would be, look in the Backups directory, see when your most recent backup is from, and confirm its recent.
Then, assuming so, you could delete the files in your Database directory (after you have backed it up just in case!)
Note that the Files/ subdirectory is image files captured, so you probably don't want to delete that.
(and some of the files in the Database directory are themselves alternate backup files, but let's ignore that for now).
After you delete the files in that Database directory (ClipTable.* and GroupTable.*) try restarting CHS and letting it start with a blank database.
Then go to the options and the maintenance tab and try to restore a recent backup in your Backups directory.
Meanwhile I will test the latest version here on my old database to see if I broke the upgrade process recently.