Hi Rosina,
Check whether you have activated the feature PPMOD after you have included your new employee group for posting.
But your saying that wage type which you have entered in IT0008 is not coming to payslip. for this first, you check whether that wagetype is available in RT (result table ) in payroll log after runing the payroll.
if it is available in RT then you need to check your payslip configuration.
Regards,
Dinesh