Please ensure that your new NVIDIA professional graphics card is seated properly into its slot. 

If your NVIDIA graphics card has a fan, please verify that it spins when the system is powered on.  

If your NVIDIA graphics card requires a supplemental power connection, please verify that the power is connected properly.  Power to your graphics card should be dedicated, not shared with another component.   

Please keep in mind that a display image is sent to only one output connection on your new NVIDIA graphics board during boot, so if you only have one monitor connected, and you are not getting a display, it is advisable to power down the monitor, and then switch it to the next output connection on your NVIDIA graphics board, and then power up the monitor again. If you are still not getting a display, repeat the steps until you have tried each output connection on the NVIDIA graphics board.  An even better option may be to connect multiple displays instead of only one.

Connect only 2 cables to the monitor:  a power cable, and the signal cable connecting it to your NVIDIA graphics card.  

In the OSD menu for your monitor, verify that the appropriate input or source (example: DisplayPort 1) is selected.  

It may also help to use a different adapter and/or cable to connect a different make and model monitor to your graphics card, to eliminate the chance that the issue is due to a problem with the monitor, cable, or adapter.

As a troubleshooting step, it may be helpful to insert the NVIDIA professional graphics card into a different computer, and/or try a different graphics card in place of the one from which you do not get a display.  

If there are other cards in other slots, it may help to remove them temporarily, as a troubleshooting step.