'New Indirect Row' button in timesheets is used for entering indirect time entries by resources.
In Administration - Timesheet Options, there is a check to disable indirect time entries so make sure the check box is not enabled if the resources are supposed to enter indirect timesheets.
Why is the 'New Indirect Row' missing in the timesheet page for all users? The users have all the required rights in the system to enter time and is also allocated to projects.
For Indirect Time Entries to be enabled, there should be atleast one charge code in the system which is Open for Time Entry because the description field cannot be left empty while entering indirect time entries. The description field is the list of charge codes in the system which are Open for Time Entry.