We have a scenario where a specific Roadmap does not load for a specific user only. It loads for an admin user, and for other users. In addition, the Roadmap loads with the same account if tried from outside the company's VPN.
The Roadmap was set to load the Timeline view for this specific user. And in "View Options" of the Timeline view, the Start Date was set to 2010. The Start Date in "View Options" was changed to Roadmap Start Date (which was set to 2021), to resolve this issue.