Need help diagnosing a hardware issue, please!

I have a PC that is roughly a year old.
The specs are:
- 400W PSU, Office Series LC500-12, ATX v2.31, 120mm fan, PFC
- Intel Core i3 6100 3.70GHz Socket 1151 CPU
- industrial Voyager 2 case
- MSI H110 Socket 1151 Motherboard P/N: H110M_PRO-VD
- 1x8GB DDR4 2133 MHz Kingmax RAM
- 240GB AMD Radeon R3 2.5'' SATA III SSD
- Toshiba 1TB SATA 3.5'' HDD
- DVD-RW

After a standard shutdown and normal usage, the following occurred:
Upon the next boot, all the usual sounds occur (specifically, I can hear the DVD drive spinning), all the fans spin up, the motherboard LEDs are lit, and the power cable to the SSD shows light,...
What isn't working is:
The keyboard and mouse combo from Logitech (not even a single light comes on),
The monitor (absolutely no signal detected),
The Ethernet port on the motherboard has no link lights,
The Power button light won't turn on,
The Reset button doesn't function either...
It shuts down if I hold the Power button down (admittedly, it occasionally boots up on its own without me touching anything 😢)

During startup, there were no motherboard beep codes or alarm sounds.

Here is what I have attempted (aside from sighing deeply at my own helplessness):
- Cleaned the contacts and tried moving the RAM stick to a different slot—nothing;
- Tried swapping out the SATA cable for the SSD—nothing;
- Tried plugging the SSD into a different SATA connector—nothing;
- Disconnected everything except the SSD—nothing;
- Cleaned the CPU fan and reapplied thermal paste—nothing;
- Threw in an old PCIe graphics card—nothing;
- Attempted to boot with only the HDD connected—nothing;
- Attempted to boot with only the HDD connected, removing the SSD—nothing;

I can't figure out what the culprit is. Everything is still under warranty, but I am stuck on what specifically to file a claim for.

It seems likely that the motherboard is the issue, considering the voltage is reaching it, yet there are no link lights on the network port and no POST beep codes to indicate any other specific hardware failure...

Can anyone suggest what else I should try, given that I don't have any spare parts lying around to test and pinpoint the exact failure?

The only thing left might be testing a different power supply, but I still need to see if I can find one... I don't have anything else, no spare 1151 processor, no extra motherboard, no DDR4 RAM... ugh.

So, yeah.

Tried swapping in a different power supply... still getting the exact same symptoms.
The PSU isn't the culprit—checked and verified!

It’s most likely a motherboard issue—I ran into something similar when I picked up my last one used. It wouldn't recognize the keyboard, mouse, or any of the USB ports, which actually prevented the PC from even booting up. A hard reset worked for me—specifically, clearing the CMOS using the motherboard jumper. Link shows you
how to go about it.
Check your motherboard manual to find where the jumper is located; if that doesn't do the trick, try replacing the CMOS battery.

LP

Try booting the motherboard naked—just the board and CPU. You can leave everything else unplugged, including the front USB ports, LEDs, and keys (though you might want to keep the power button and that little speaker connected just in case). I guess it’s best to start without any RAM at all to see if the speaker gives you an error code or something. Also, maybe reset the BIOS to defaults first by pulling the battery or using the jumper.

Alright, I’m jumping on every single suggestion the second I get near the machine! Thanks!
Basically, I'm looking at a full CMOS reset, pulling everything except the CPU, the motherboard speaker, and the power button, and then seeing if it actually boots...

Hey everyone, I’ve actually made some progress thanks to your help... Right now, I've just got the power cable connected—no RAM, no hard drive, nothing in the slots, just the processor. Now I'm getting an alarm sound... three long beeps! What's the move here? Should I just start stuffing in whatever components I have on hand and see what happens?

By the way, I don't see any jumpers on the board like the ones shown in the video, but I did pull the battery out for about a minute.

Thanks, everyone!
You guys really saved me from making a massive mess out of a totally invalid warranty claim... Aside from those two front-panel USB 2.0 ports on the case, everything seems to be functioning perfectly (though I probably just had a momentary brain fart with the motherboard cables)...
I went through a step-by-step check with all my peripherals—scanner, printer, webcam—plus the two standard HDDs inside the chassis, and everything checked out fine...

The first round of beers is on me! Just let me know when we finally cross paths!

So everything's working? Great...

Everything is working fine, except for the power button occasionally flickering on and off... Even though I’ve checked everything and every single connection seems to be seated properly...
I say "seems to be" because both the motherboard and the case are MSI, and those connectors are incredibly loose... I'm actually considering ripping them out entirely; I'm worried that "maybe it works, maybe it doesn't" contact might end up shorting out the motherboard...
One of the front USB 3.0 ports is dead because one of the tiny wires on the motherboard header snapped—specifically for that blue USB 3.0 cable...
So, yeah, things aren't exactly perfect, but let's call it a solid 80% success rate! 😉
Thanks again...

fadedorca66 said:Try booting the motherboard naked—just the board and CPU. You can leave everything else unplugged, including the front USB ports, LEDs, and keys (though you might want to keep the power button and that little speaker connected just in case). I guess it’s best to start without any RAM at all to see if the speaker gives you an error code or something. Also, maybe reset the BIOS to defaults first by pulling the battery or using the jumper.

Exactly. With just the board and the processor, you should hear a long beep indicating it's crying out for memory.

That’s a pretty shaky DIMM slot you've got there. I’d suggest testing each stick one by one to confirm if they're all actually working; if they are, then you know for sure it's just a loose slot. I have a Dell setup running an Intel Core i7 that's in a similar boat. I was thinking about selling it, but honestly, I'm hesitating. You never know—one little bump to the RAM and... everything goes black.