Hi Mohd,
Please check below SAP note
SAP Note 926290 - SWNCCOLL: SAP workload NW collector collects no data
Additionally check the below
1) executing TZCUSTHELP (system time zone) && TZONECHECK (client time zone) , compare both are in sync or nor if not then do make the necessary adjustments
2) Execution of standard jobs (SAP_COLLECTOR_FOR_PERFMONITOR...)
3) Execution of SAPOSCOL
Hope this helps.
Regards,
Deepak Kori