bios setting cpu display only for dual monitor
AE did not recognize the nvidia card gtx 980 but recognize intel display card onboard
but it was detected in Cinema 4D
if bios setting to PCIe display for one monitor
AE works fine with GTX 980
so ，it is a way to force AE to choose a display card ？
Sorry to hear about your trouble. Hopefully, someone with your hardware setup will chime in. As you know, these configurations are unsupported for use with After Effects.
Where are you looking to have AE support that card?
AE uses the GPU very differently for different functions and often it'll say unsupported for one thing that doesn't matter, but it works everywhere else. (Also keep in mind that AE doesn't use the GPU for very much.)
If you're looking in the ray-traced renderer settings, can you tick the "use unsupported cards" option?