When Your Dog Will Not Sit

A dog used to receiving a vocal “Good” as well as a treat of petting or food for fetching a ball

might be gradually less likely to fetch on command without any petting or food reinforcement.

Dogs learn by repeated behavior. You may also find that a dog may be less likely to complete a trick or tasks if a previous reinforced behavior is no longer used. This can be a reason for a new pet being unable to learn or complete a trick.