Page lists all projects and tasks for which the current user has at least read permissions.
Reasons for not being able to log hours (missing input field) include:
Project/Task is closed
User is not a member of a task
System Parameter "TimesheetLogHoursOnPotentialProjectsP" prevents logging
System Parameter "PermissiveHourLogging" prevents logging
System Parameter "LogHoursOnSolitaryProjectsP" prevents logging
System Parameter "LogHoursOnParentWithChildrenP" prevents logging
Timesheet-Workflow (Package: intranet-timesheet2-workflow or other WF) prevents user from logging hours