Samsung C24F390 monitor detected by laptops but display is blank

[Hampo]

My three year old C24F390 has started blanking out and cycling continuously between HDMI and AV input icons in the top left.

It does this when connected via HDMI to both a Windows PC and a MacBook (via a USB-C adaptor). The laptops are recognising there is a monitor attached (it shows in settings, and windows disappear off the laptop screen) but the screen is blank and won't display the input.

When it's blank and cycling through inputs, the menu button won't work. It will display but then will drop out of the laptop moves. Sometimes it won't detect on startup.

I've tried a couple of HDMI cables, including a brand new one.

[alaut]

I actually have the same exact issue. Funny coincedance for a very old monitor and both recently having this issue.

For me, I do use a dock but that doesn't seem to be driving the problem. The laptop itendifites all 3 monitors, but the laptop screen and other brand screen work fine, but the samsung screen remains black even though I can move windows offscreen and you can tell it's rendering behing the scene. I can drag a window partially off-screen, into the black, release, and then regrab in the black if I position the cursor correctly.

It's a big nuisance as it cycles sometimes between analog/hdmi and the menu doesn't work to restart while doing this.