User is unable to view some projects in the Time Entries screen.
This can happen if the projects have a status other than Active. Only active projects and items display in screens and lists. So you need to change their status to Active before they are visible in the Time Entries screen. Check out this article for details on how to do that: Making inactive projects active.
Note: If you have team members assigned to the projects, you should make sure to include and assign all employees that should be working on them. Only the team members assigned to the projects can make time entries on them. Check the Core Help for details.