Hi Rajendra,
Share the snapshot of transaction /IWFND/MAINT_SERVICES where your launchpad services are added. Make sure the system alias is LOCAL. Check here : SAP Fiori LL18 - System Aliases definition for Fiori
Also I don't understand, you are trying to implement Order From Requisition app and above solution given were for PO approval which is different. Are you sure, your errors are resolved ?
Service sra013_po_from_pr_srv is for Order from requisition app.
Backend role to be given : SAP_MM_PURORD_OR_APP
Regards,
Tejas