7920T w/ OEM Nvidia RTX A4000 not outputting at 4K

Purchased from Dell 7920T with Nvidia A4000 pre-installed, I've been asked to fix the dullness of its output to a TV, Samsung UN55TU700DFXZA.  I'm using a DP to HDMI converter as the TV has no DP.  I already know TVs make for bad monitors, but I've been asked to get this to output to the TV at 4K.  The NV drivers I've used were supplied by Dell.  The Windows Display settings never offer a resolution above 1920 x 1080.  NV's data sheet for this display card says, "Max simultaneous displays 4x 4096 x 2160 @ 120 Hz"  The other 3 displays are running at 1920 x 1080.

What am I overlooking?