I apologize for not getting back sooner. All the answers were relevant, but the problem was really related to my lack of familiarity with the new ASUS monitor PA248. The display should have come up automatically, but for some reason it takes more than a few seconds to recognize the HDMI port and I started trying to select the HDMI using the monitor menu. To make a long story short it appears to be a combination of the delayed port recognition and my lack of knowledge about how the monitor works. The interface is now working properly. The documentation for these new products could be improved significantly.
Thank to all who responded.