Not a lot of information to go on. Please attach your model that the error occurs in and describe using a Screencast what you are trying to to. If you do not know how to attach your Fusion 360 model follow these easy steps. Open the model in Fusion 360, select the File menu, then Export and save as a F3D or F3Z file to your hard drive. Then use the Attachments section, of a forum post, to attach it.
"If you find my answer solved your question, please select the Accept Solution icon"
John Hackney
Retired
Beyond the Drafting Board