I tried the troubleshooting given here, but I can't get very far.
https://forum.arduino.cc/index.php?topic=107098.0
This is my Arduino:
It uses the ATmega16U2 so I didn't think I'd need to update the drivers. Nevertheless, I've tried updating drivers on both my PC and my Mac. No matter what I do the little bugger what show up in Ports on Arduino IDE.
Any ideas?
Does it show anywhere in Windows device manager?
Did it work before?
Are cables properly inserted at both sides?
Have you tried other cables?
All the cables are properly plugged in, the Arduino even gets power. But it doesnt show up anywhere
It should show under COM & LPT PORTS under windows at least.
If you don't see that category in device manager and are using windows 10, then ensure you turn on SHOW HIDDEN DEVICES.
Some installs of win 10 do not enable the com port by default.
BTW some devices don't like USB 3.x so where possible use a USB 2.0 port.
There is only "Arduino Dew (COM3)" under Ports (COM & LPT). It has a Yellow '!' sign. But it is always there, no matter if the Arduino is plugged in or not.
My other Arduino shows up and its using the CH340! So odd
Ive been trying to use a work around to program it. I have a second Arduino, I follow this guide
But it also threw up errors in IDE
0_0
It sounds like the yellow sign you are seeing is cause by something else and you should fix that first in case it is something related to the USB ports.
Once that is fixed then re-run the checks and tests you have done again and let us know if there is any improvement.
It sounds like your computer may not be fully set up with correct drivers or has another issue.
Bob.
Its happening on my Mac too.
Also, I just fixed the yellow sign by adding legacy hardware via Actions on Device Manager.
Still have the same issue : /
Maybe the Arduino is faulty?
Can I presume you did a full re-boot of the computer after making the changes to fix the yellow sign ?
If you did then it is possible you did some random damage to the board.
Possibly you have a bad board, or the ATmega16u2 was not programmed properly. Burning the bootloader to the atmega2560 will not help, the atmega16u2 is the USB interface and should show up even if the 2560 were removed.
Try a different USB cable, that particular cable is rarely a power-only cable, but it is a possibility.
I forgot to reboot :o but nevertheless, it still doesnt show up. I even downloaded an Arduino Program on my Android phone, but like every other device, my phone powers it but it doesnt register anything is connected to it.
I could have damaged the board I guess? Or it could have come to me damaged? Who knows, your guess sounds better than mine, but after 3 devices, 5 hours of troubleshooting, install drivers from multiple sources, stuffing around inside Device Manager as Admin AND trying to program the Arduino via another Arduino (i.e. the second Ardunio wasnt even plugged into the computer). Im out of ideas.
Funny that it throws up errors in IDE when its running through the second Arduino too. My hunch is that its faulty.
@David_2018 It could be the cable maybe? Unfortunately I dont have another printer cable around to test
Received My mega board today and It would not recognise it on the PC, found an old topic on the forum and it solved the problem. Was thinking that I had a duff board, but hey it now works.
what was the topic ? (link please)
Strangely enough it was one of your posts.
https://forum.arduino.cc/index.php?topic=354875.0
the driver download from this.
LOL 
Glad to be of assistance even if I didn't know it !
You're welcome and thankyou. I have only just started out on the Arduino journey, and to have people to help is a blessing.
Karma for doing some homework.
Just a little update
I got a new board today and it instantly worked.
Thanks for all your help Ballscrewbob (and others)