Dell E2420H monitor not detecting video signal

I have a Dell E2420H monitor connected to a laptop running Windows 11 Enterprise via a docking station.  The external monitor only intermittently detects the video signal from the laptop.  All the power settings are correct for the monitor to work when the laptop lid is closed.  I can sometimes get it to work after a reboot.  It will usually work for a couple of days then the monitor goes black again.  Any suggestions?

Ray Porter