Thanks Frank.
That is the exact issue. HP shipped the monitor with an HDMI cable, Nothing for displayport. From what I found in PDA files on online, there should have been a VGA cable as well.
I'm very surprised that after I worked with an HP sales rep to purchase this monitor & tower, that HP would ship it without any way to connect the two.
I spent some time emailing & talking on the phone until they agreed to send an adapter without additional charges.