Hi ,
In Twinmotion 2023.1/Unreal Engine 5.1, Path Tracer support for NVIDIA GTX cards, like your GeForce GTX 1070, was removed due to instability with the Path Tracer enhancements in this version, To use Path Tracer in Twinmotion 2023.1 going forward, you will need to upgrade to a compatible GPU (AMD Radeon RX 6000 series or newer or any NVIDIA RTX GPU).
You can continue using Path Tracer in Twinmotion 2022 with the GTX 1070 as these versions will continue to support Path Tracer on these graphics cards.
Best,
Raghib