This would be to ensure that you are registering your athletes to your provincial governing body.
Go to Setup - Sessions - Schedule
And look under the Reg Cat column - all classes should have Recreational Artistic Athlete showing up on each line. Triple check this.
If the category is attached to each class correctly- then go to Setup-Setup Fees
Click on the Category Column - once it is sorted alphabetically, check to make sure that you only have ONE category per FEE. If you have more than one category setup with a fee, fix this - this is what is probably causing your error.
If the category is NOT attached to each class correctly - then go to Setup - Select Categories
Click on Search All, and select all categories that apply for your club. Click Save.
Then go back to Setup - Sessions - Schedule
and attach the correct categories into each class and click save.
Then go to Setup Fees to make sure you only have one fee per category setup correctly.