Sometimes when you tweak the CSS in the project settings if there is an error, it can really upset the build process that generates the preview. Once the errors are fixed it can still take several minutes for the build to complete what it is doing and allow things to work again.
Here is a quick guide to help you get back on your feet.
If you have a CSS issue, to help you discover the problem debug information is now available. This will automatically appear as an error message when the "Preview course" button has been selected. When the error message is shown simply select the arrow (1) to reveal the snippet of code that is causing the problem.
Once you have fixed the CSS issue a great way to give your Adapt Authoring tool the equivalent of a jump start is to select the arrow (2) next to the “Preview course” button, then select “Force rebuild”. This will force Adapt to rebuild your course.
If you are sure you have fixed the CSS and the preview is still broken after 10 minutes please get in touch via [email protected] and we will see if there is a more significant problem.