ST2010B, Windows 10, stuck in PSM (Power Save Mode)

I've had a Dell ST2010 monitor hooked to my SONY laptop for years.Recently I developed troubles. On bootup, the monitor enters Power Save Mode, within a couple seconds of startup, and sits there. I have no idea how to keep it from doing this, or how to get it out of that mode. So I'm stuck using the smaller laptop screen. Can anyone here help me to fix it, or to simply  get the monitor to "never" go into Power Save Mode? The problem began last week, after a couple Windows 10 updates from Microsoft. In an effort to fix the situation, I did a system restore to two weeks back. Voila, the monitor was usable. But in continuing to use the computer, Microsoft noticed that my Windows was up not up to date, and threw me the updates. No more monitor. Furthermore, Windows 10 does not keep many Restore Points on my machine. Just two. And now I have only a couple from this week. Anyway, that's what I think happened. A local computer repair-person tells me that he's gotten many reports of external monitors going belly-up this way in recent days.