[SOLVED] [SOLVED] Did the RJ45 port of my new motherboard kill my modem-router?

[Amaryl]

This will sound ridiculous.

I have a new build with an asus tuf gaming x570-plus wifi motherboard, whose BIOS I can't update using a CAP file downloaded from the official website ("Is not a proper BIOS" message, and yes I formatted my usb key in FAT32). So I wanted to use the feature that allows updating the bios through the internet. I usually use the WIFI only, but I figured I had to have the RJ45 connected for this operation. When I connected the RJ45 (for the first time ever) and attempted the update, it failed. Then I realized I had lost the internet connection on all my devices.
This is a modem-router from my ISP (VOO, Belgium). I connected to the web interface of the device and it says the Internet connection with the provider is established, but I can't get any internet either through the WiFi or an RJ45. I tested with my new computer, with a laptop, and same thing with my smartphone.
I did reset the device to the factory settings, but it didn't help.
I called the support, did eveything they asked me to do, and they said everything seems fine from their side., that I should have internet working. They will send a technician tomorrow evening.

My stupid question is: is this only a coincidence, or is it technically possible that something related to the RJ45 port of my new motherboard or anything related to the BIOS update I attempted, broke something in my modem-router?

 

[Amaryl]

It turned out when the tado box is not connected to the electricity, but connected to the modem-router via RJ45, it messes up the router.

It happened precisely at this moment, because I cut the juice to the tado box to plug the computer next to the router instead.

Still this is a strange thing, but problem solved.

 

[Ralston18]

I would think not - more likely a configuration error. However, a physical problem, e.g., failed ethernet cable or port, cannot be ruled out.

Curious about " So I wanted to use the feature that allows updating the bios through the internet." What website did you connect to; ASUS?

Make and model of ISP provided modem/router?

On your new build - are you sure that only one network adapter (either wired or wireless) is enabled? One or the other only - not both.

Have you tried other, known working Ethernet cables between modem/router and other wired devices?

Are you able to run and post the results of "ipconfig /all" (without quotes) via the command prompt?

 

[Amaryl]

Thank you for taking the time to answer @Ralston18. I have just found the solution and posted my answer at the same time as you did. See the one just before your message.

It's kind of stupid, but I think I have the right to be surprised by what caused the problem.

Again, thank you for your time.

 

[Ralston18]

You are welcome.

However, just in case, if you power on the "tado" box and the problem re-occurs then look for an IP address conflict.

Could be that the tado and router have the same default IP address.