This issue is usually caused because of the users' permission settings.
Follow the steps listed below to check the permission:
Log into Web TimeSheet with Administrator rights.
Identify the permission assigned to the affected user, (edit the User profile -> Access tab -> Permissions)
On the left side menu, select Permissions. From the permissions list, edit all permissions (one by one) that you found enabled for this affected user , expand Timesheet sub-permission. Make sure the entry Allow time to be entered is enabled.
If this option is disabled, then the users can only see their timesheet, but won't be able to make time entry.