HDMI output stopped working all of a sudden

[Jarstab]

My laptop is connected to:

Samsung 24" screen from laptop USB-C to HDMI converter and then cable with HMDI --> DVI, whereas DVI is input in monitor.

Samsung 49" ultrawide 3840 x 1080, from HDMI port on laptop to HDMI input on monitor.

Was working fine for months.

Then 49" monitor stopped working. Is not detected anymore by PC. If I try to boot with everything connected, booting haults before loading Windows. If I unplug, boot continues.

When booted, if I plug back USB-C converter, no picture shows on 24" monitor. Windows does not detect monitor. But if I then plug back the HDMI cable to the 49" monitor, the 24" monitor starts displaying, so 24" monitor is then detected.

Think I have updated all drivers, BIOS, chipset, graphics card etc. Tried 15-sec reset of Laptop.

What else could I try? Both monitors works well on other computers.

Device Manager shows one Generic PnP Monitor, and one Pnp-Monitor (Standard). The last one is listed with an exclamation mark. Tried updating drivers etc...

One more thing, when uplugging the HDMI monitor, the monitor says "no cable", so seems like there are some communication between laptop and monitor.

Can also add that the screens working (24" + laptop) flickers quickly like once every 10-15 minute, just as if windows detects a "monitor change". Like what might happen normally when unplugging/plugging in a montor.

[Jarstab]

Seems like nothing is helping - I belive this could be a HW issue.

HP want to change the motherboard.