Thanks for your quick reply. However, I have actually tried all that with no luck. A bit more information: This is the second monitor (and yes, I know how to use the Display Settings to connect a second monitor, which I have done in the past.) I receive these messages: "No HDMI 1 signal from your device. Pressany key on the keyboard or move the mouse to wake it up. If there is no display, press the monitor button to select the correct input source." I have done this also, and HDMI 1 is selected. Then I get "No HDMI 1 signal from your device." I'm thinking that the older (2015) CPU may have a different version of HDMI than the current monitor. Other ideas?