There shouldn't be any incompatibilities. That is a dual socket board. If you only have a single CPU, you need to verify that you put it in correct socket for a single CPU.
Also the PCIe slots are mapped to specific CPUs. There is a section on PCIe in the manual --
https://www.intel.com/content/dam/support/us/en/documents/server-products/Intel_S2600ST_TPS.pdf
If you have a single CPU it has to be in the socket closest to the front of the motherboard.
Only PCIe slots 5 and 6 (closest to the CPUs) are mapped to CPU#1.
Below is the response I received from Nvidia support chat:
Yogesh Chauhan: We purchased the Motherboard Intel Server Board S2600STBR
Yogesh Chauhan: and with this we opted for GPU ASUS GT730 2GB DDR5
Yogesh Chauhan: While configuring the GPU with this motherboard my vendor said that this GPU will not work with this motherboard.
Yogesh Chauhan: Can you please help me with it, because as per our vendor this is our waste of money as we can not use this.
Swathi: Ok
Swathi: Is it installed on this server?
Swathi: Does it give you any error, or not working at all?
Yogesh Chauhan: It gives blank screen
Yogesh Chauhan: No display
Swathi: Ok previously was there any other card installed on it?
Yogesh Chauhan: No
Yogesh Chauhan: This is a brand new server
Swathi: Ok , Yes for this card there are no drivers for servers
Swathi: Its only for windows pc and linux
Yogesh Chauhan: But on server we have Window 10 and Ubuntu
Swathi: For server support we have quDRO rtx series and quadro series only