Ext Motion Flood Light (New) - 1 light not working???

I recently replaced all my exterior motion sensor flood lights. The old lights worked fine other then the senors were going out. So you know, all light installed locations are under eave with a electrical box and standard wire already run to each location. All wires were in good condition. New lights were installed with proper size wire nuts and secured with electrical tape. The front driveway light was installed and works fine. This light is a different brand from the backyard lights. Backyard flood light (1) installed easily and works fine. Backyard flood light (2) installed easily BUT only one of the bulbs came on. :confused::confused: I replaced flood light (2) with another new light and the same problem occurred. I swapped the bulbs (ALL new) showing me the bulbs were not the issue. :wall: One difference between both backyard flood lights is (1) has 4 wires (2 blk, 2 wht) where (2) has only 2 wires. My thought is one of (1) pairs runs to (2).