Product support page:
https://support.hp.com/us-en/product/details/hp-e24mv-g4-fhd-conferencing-monitor/34513971
User manual is showing that at 1920x1080, the monitor has a refresh rate (vertical frequency) of 60 Hz (page 30). So that seems unlikely to be the issue.
After you plug in the monitor or the dock, have you tried generating a few keyboard or mouse events (like pressing the Shift key, or clicking on the mouse pointer in a "harmless" area)? I believe the Mac will check for the presence of monitors only at a few specific times. And the monitor itself may have entered a sort of sleep state if it was not receiving a signal.