Mac Mini will not wake up monitor

I have a new 2020 Mac Mini (received it last week) hooked up to a 27" Dell UltraSharp monitor via HDMI and using Apple wireless keyboard, trackpad and mouse. This morning the Mac will not wake from sleep. I've tried powering off/on the display, swapping out the HDMI connections, and still nothing. The Mac beeps when I hit the return key a number of times. Any suggestions?