I have a Surface Pro 4 connected to a Surface Dock. SP has the latest updates; Dock has the latest firmware. SP power setting is to never sleep when connected to power.
When I connect any Dell monitor ( I have tried 3 different models) to the Dock, SP screen keeps flashing a black screen and nothing appears on the Dell monitor. When I connect the monitor directly to the SP using a VGA / Display Port adapter, SP shows 2nd monitor as not active; monitor says that there is no signal from SVGA and immediately goes into power save mode.
I have gotten this to work by turning on the SP and logging in.
Remove both power and display cable from monitor.
Reconnect power cable, wait until monitor reports that there is no signal and it is going into power save mode in 5 minutes.
Reconnect the video cable and "all's right with the world".
Client feels this is an unreasonable work around. (joke.)
I cannot find anyway of disabling powersave feature on the Dell monitor.