I have (or would like to have) three profiles:
Laptop Only (3200x1800)
Home Dual (3200x1800 and 2560x1440)
Office Dual (3200x1800 and 1440x900)

The first two work fine. But for some reason Win 10 sees but will not activate the second office monitor. It's a cheapo old Samsung and it's in sleep mode, the power LED is blinking. In the Windows display dialog, the second monitor is shown in gray and it will not show any resolution options. Trying to Apply either Extend or just clicking Identify results in my main display going blank until it times out.

Even more confusingly, if I try to create a new Office Dual profile, Display Fusion apparently copies the Home Dual profile. Even though the second monitor is disabled, it shows the 2560x1440 resolution in Display Fusion.

I've read the Samsungs do this if the computer is trying to set an incorrect resolution, so I'm wondering if Display Fusion is somehow trying to apply the home secondary's 2560x1440 resolution to the office secondary?

They sure did screw things up in Win10. Oh and the drivers are current (Intel 5500).

I have also installed the correct INF for the monitor. Now it shows the brand and model in Device Manager but it didn't fix anything else. Interestingly choosing to clone the display between the two monitors also results in a blank screen on the laptop until the "are you sure" times out (the secondary doesn't change states).

I was getting the same results in the Windows Settings dialogs. (And yeah I kind of figured it was more likely a Windows problem than a DF problem!)

However, I switched to a DP / DVI cable and for whatever reason it now works as expected.