Based on the screen shot that you uploaded, it appears that H.265 encoding using CUDA, IS enabled
only decoding is software. If I remember right, I recall reading somewhere on the forum that H.265 hardware decoding requires Pascal
architecture which I think is only present on the
GTX 1050 and its successors (1060, 1070, etc.) in the 1000 series. But then you said you used it before with your 980 card. You might want to temporarily reload an older video driver that worked with hardware decoding and see if can be enabled. Also, did you try unchecking the "Enable Lighting Shrink ..." box and manually selecting CUDA?