What can be checked that has caused the low beams even with newly replaced bulbs working on daytime running light voltage on low beam but fine on high beam ground fuses and sockets fine?

You can check the ground in the wiring if nothing else works. However, it would also be a good idea to see if you are just making a simple mistake. Sometimes the light-on switch is separate from the hi-beam/lo-beam switch; try pulling back on the turn signal lever while the light is on. It should switch between hi and lo beam.