Optiplex 7010 (2013) Radeon HD 7570 - desiring 1440 (2k) resolution

Just upgraded our 22in monitor (1080p ) to a LG QHD capable of 1440p  (2k) @75hz

We have a high quality DPI-to-HDMI cable that is capable of transferring 4k @120hz res video.  When we hooked up to the new monitor, Windows only shows max res of 1080p.   I installed the latest Radeon firmware ("lagacy" from 2015), and this did not change what Windows shows as max res (of 1080p)

What would I need to do to see the Windows option of 2560x1440p resolution?

* I know the cable works and monitor supports 1440p - I used a laptop from work (used an older HDMI-to-HDM) to confirms the monitor can display at 1440p. 

Thanks.

Thanks in advance?