Error loading Demand Roadmap.
Changes made to Timeline Visualization record.
The behaviour seen is due to the changes made to the Timeline Visualization record 'Demand Backlog' seen here:
Notice how the Lane condition is currently blank. In an OOB instance the default condition for this field is:
Portfolio.Task type - is - Portfolio
This is not necessarily the condition that will need to be used, this is just an example of why this roadmap is not loading properly. Please update the lane condition to test the solution. Here is further documentation on creating Timeline Visualizations: