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Hello thank you for taking your time to help, any help is really appreciated  :)!

I just finished building my mining rig and everything seems to work fine, but only 3 of my GPUS are powering up. I am currently at the Bios stage and haven't downloaded any OS yet. I am planning on downloading the OS after I am able to power up all the GPUS. The parts I used pertaining to powering up the GPU are:

1. EVGA supernova 1300 G2.
2. these PCIE risers https://www.amazon.com/gp/product/B01GU94QSQ/ref=oh_aui_detailpage_o00_s03?ie=UTF8&ps (https://www.amazon.com/gp/product/B01GU94QSQ/ref=oh_aui_detailpage_o00_s03?ie=UTF8&ps) from amazon.
3. MSI Z170A Pro Gaming Carbon.
4. 5 XFX Rx 480 8gb + 1 Sapphire nitro+ rx 480 8gb.

I plugged in 6 individual 8pin cables from the 6 VGA ports of the PSU to each of the GPU and thought that this would be the main power source. I noticed that my PCIE risers also had a Molex to SATA adapter which I read online to be an extra power source and was not really necessary, however, it seems that only the GPUs that utilize the Extra SATA power source powers up. My Psu only comes with 4 SATA ports and 1  is being used by the SSD, and as result only 3 of my GPUs are connected to the SATA. Each SATA cable has multiple SATA ports in them and I was wondering if I can connect 2-3 GPUS on a single cable to power up the rest of the GPUs.

I've also read online that SATA cables shouldn't be used to power up GPUS as they don't have enough Amps and that I should be using Molex to 6pin adapters instead.

What am I doing wrong and what are some steps I can take to fix this problem! Thank you once again.

You'll have enough power to get it going, but I'm not sure if you'll have enough power to sustain mining. Unless you undervolt it. You can have 3 power risers on one sata cable as long as you have 3 sata power plugs on that cable. Basically, you can run multiple power risers and ssd off of one cable. The power needed is minimal.

You will need everything powered (8pin + power riser via sata) before your cards will power up. It sounded like only 3 gpus are connected to the sata - that would be why you only see 3 cards (if i'm reading it correctly). You also need to make sure that your settings are right in your bios. MSI Z170A - http://1stminingrig.com/msi-z170a-gaming-pro-carbon-motherboard-review-mining-performance/ This might help on settings.



 

I advise no more than 2 PCIE risers on 1 Sata cable if you must use adapters. However I only advise that if you have no other option of powering your risers. Adapters are just another failure point plus you can overload the sata power cable if you are not careful but you should be ok with that limit on an EVGA PSU. I do not recommend plugging in 2 gpus + 1 SSD on the same sata cable.

If you are having cards not powering up, define not powering up. Are the fans not spinning or is the card just not being recognized at all?

I recommend you rule out faulty risers by switching the "dead" cards to another riser and see if they power up.

This tutorial may give you some other tips or help - http://1stminingrig.com/tutorial-ethereum-mining-rig-part-1/

As everyone else has pointed out, you definitely do need all the risers plugged in. Also you're perfectly fine plugging in 3 GPUs on 1 SATA cable because 3 graphics cards are going to pull ~12 amps (~4 per card) thru that cable at 12V, and the EVGA cables are plenty thick gauged enough and EVGA has a single 12V rail shared between the ports.