If you stopped getting scrap metal/wires for winning PvP battles, we recommend you to check if you had reached the weekly limit for these resources:
Scrap Metal: 3500 units per week
Wires: 2800 units per week
Batteries: 1400 units per week
Please note that the limits do not take into account the resources that were earned in the daily tasks, obtained by parsing the items, purchased on the market or exchanged for the Mechanics badges in the Workshop. The limits are updated every Monday. You can also increase the limit for the resources received when purchasing a Scanner.