I apologize if this is the incorrect place for this. I'm trying to fix my mother's home PC which she wishes to use to work from home on some days. It was built a few years ago - I don't remember when exactly - and was used for a little while without issue before she started to use a laptop in a different room as her machine of choice. For whatever reason the machine was left idle for about a year, then was switched off.

>Specs
Ryzen 5 3600 XT
2060 Super
Asus Prime X570-P
Aorus 32GB RAM. Unsure of model, speed CL timing etc
M.2 SSD
Win 10
2 Dell business monitors

>Symptoms
Motherboard LED glows fine when PSU is switched on
When main on/off switch is turned on, all fans, CPU graphics case mobo, spin up as normal. RAM LEDs glow.
Monitors do not detect signal from PC. It seems as though they attempt to, as they don't display a message about going into idle mode if no source is recieved while plugged in, but simply say that no signal is recieved from the source.
NO POST BEEPS. There have been no POST beeps of any kind during each power on.

>Attempted fixes
Disconnecting all peripherals and running only with PSU power in and video cable(s)
Attempted 2x DP, 1x DP on each monitor by itself, 1x HDMI on each monitor by itself, all plugging into graphics card. Same result each time. Also attempted HDMI into mobo but I know the processor doesn't have graphics
Reseating RAM
Running only a single stick of RAM in case the other is bad, and swapping
Above but in different slots
Reseating graphics card
Removing CMOS battery and leaving it out for ~20 minutes before reinserting

>Things I haven't tried, yet
Seating graphics card into different PCI slot
Using different internal cables

>Other
I've tried plugging her laptop into the monitors via HDMI and it displays without issue

Please help