First, reset the BIOS to reset the hardware tables.
Power off the unit, switch the PSU off and unplug the PSU cord from either the wall or the power supply.
Remove the motherboard CMOS battery for five minutes. During that five minutes, press the power button on the case for 30 seconds. After the five minutes is up, reinstall the CMOS battery making sure to insert it with the correct side up just as it came out.
Now, plug the power supply cable back in, switch the PSU back on and power up the system. It should display the POST screen and the options to enter CMOS/BIOS setup. Enter the bios setup program and reconfigure the boot settings for either the Windows boot manager or for legacy systems, the drive your OS is installed on if necessary.
Save settings and exit. If the system will POST and boot then you can move forward from there including going back into the bios and configuring any other custom settings you may need to configure such as Memory XMP profile settings, custom fan profile settings or other specific settings you may have previously had configured that were wiped out by resetting the CMOS.
Next, do a clean install of the Nvidia drivers, and by CLEAN, I do not mean just RE-install or just "install" a newer driver. Use the DDU and do a CLEAN install.
If there are any steps listed here that you have not already done, it would be advisable to do so if for no other reason than to be able to say you've already done it and eliminate that possibility.
First,
make sure your motherboard has the MOST recent BIOS version installed. If it does not, then update. This solves a high number of issues even in cases where the release that is newer than yours makes no mention of improving graphics card or other hardware compatibility. They do not list every change they have made when they post a new BIOS release.
Second,
go to the product page for your motherboard on the manufacturer website. Download and install the latest driver versions for the chipset, storage controllers, audio and network adapters. Do not skip installing a newer driver just because you think it is not relevant to the problem you are having. The drivers for one device can often affect ALL other devices and a questionable driver release can cause instability in the OS itself. They don't release new drivers just for fun. If there is a new driver release for a component, there is a good reason for it. The same goes for BIOS updates.
IF you have other hardware installed or attached to the system that are not a part of the systems covered by the motherboard drivers, then go to the support page for THAT component and check to see if there are newer drivers available for that as well. If there are, install them.
Third,
Make sure your memory is running at the correct advertised speed in the BIOS. This may require that you set the memory to run at the XMP profile settings. Also, make sure you have the memory installed in the correct slots and that they are running in dual channel which you can check by installing CPU-Z and checking the Memory tab. For all modern motherboards that are dual channel memory architectures, from the last ten years at least, if you have two sticks installed they should be in the A2 (Called DDR4_1 on some boards) or B2 (Called DDR4_2 on some boards) which are ALWAYS the SECOND and FOURTH slots over from the CPU socket, counting TOWARDS the edge of the motherboard EXCEPT on boards that only have two memory slots total. In that case, if you have two modules it's not rocket science, but if you have only one, then install it in the A1 or DDR4_1 slot.
Fourth,
Make sure the problem is not just a bad cable or the wrong cable IF this is a no display issue. If it is NOT related to a lack of display signal, then skip to the next step.
This happens a lot. Try a different cable or a different TYPE of cable. Sometimes there can be issues with the monitor or card not supporting a specific specification such as HDMI 1.4 vs HDMI 2.0, or even an HDMI output stops working but the Displayport or DVI output still works fine on the graphics card. Always worth checking the cable and trying other cables because cables get run over, bent, bent pins or simply were cheap quality to begin with and something as simple as trying a different cable or different monitor might be all that is required to solve your issue.
The last thing we want to look at,
for now anyhow, is the graphics card drivers. Regardless of whether you "already installed the newest drivers" for your graphics card or not, it is OFTEN a good idea to do a CLEAN install of the graphics card drivers. Just installing over the old drivers OR trying to use what Nvidia and AMD consider a clean install is not good enough and does not usually give the same result as using the Display Driver Uninstaller utility. This has a very high success rate and is always worth a shot.
If you have had both Nvidia and AMD cards installed at any point on that operating system then you will want to run the DDU twice. Once for the old card drivers (ie, Nvidia or AMD) and again for the currently installed graphics card drivers (ie, AMD or Nvidia). So if you had an Nvidia card at some point in the past, run it first for Nvidia and then after that is complete, run it again for AMD if you currently have an AMD card installed.