Do you have any visitors in your project?
Make sure that your heatmap has recorded visitors by reloading the dashboard and checking the visitor column for the project.
Are you sure your Audience is set up correctly?
Test that your audience works by opening up heatmap settings and then open a preview for the project. You do this by clicking the heatmap project -> click Configure heatmap -> click preview. Now check that audience evaluates to TRUE.
Do you have parameters in the canvas URL?
If you do get the heatmap parameters you can check if the URL you've added as canvas URL contains its own parameters. This might mess with loading the heatmap correctly so please remove the parameters from the canvas URL and save and try to open the heatmap again.