When the generation of a Mark results in an error, the invalid Mark will not be visible, and a Message is shown in the Messages drawer.
To fix the issue, read the Message closely - hovering over the message will show a more descriptive tooltip. Then, select the Mark listed underneath the Message to select the (invisible) Mark and make the relevant inspectors available so you can correct the settings.
Common errors:
A Mark can fail at three different levels:
At Document level: an issue with a Mark directly on the document. You will get a regular error message. You can fix the issue by selecting the Mark and checking the settings in the available inspectors.
For more information on Nested Marks, see Nested Marks