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.