AFAIK, PCI-E is fully backward compatible. If you have a 2.0 card fitted into a 1.0 slot, the card will operate at the 1.0 speed (physical limitation). Before sending the card for RMA, reduce the load on the PSU by having only the following installed and connected to power:
1. One RAM module
Connect the monitor to the GPU and turn on the power. If the display is shown on the monitor, then you may have an under effecient PSU. If still no display, continue with RMA.