The video ports on the MB dont show anything. Did you make progress on yours? and any tips?

CPU: Intel - Core i5-8400 

CPU Cooler: Cooler Master - Hyper 212 EVO

Motherboard: ASRock - Z370 Extreme4 

Memory: G.Skill - Ripjaws V Series 16GB (2 x 8GB) DDR4-3000 Memory

Storage: Samsung - 850 EVO 500GB M.2-2280 Solid State Drive 

Storage: Western Digital - Caviar Blue 1TB 3.5" 7200RPM Internal Hard Drive

Video Card: Gigabyte - GeForce GTX 1080 8GB WINDFORCE OC 8G Video Card

Case: Phanteks - ECLIPSE P400 TEMPERED GLASS ATX Mid Tower Case 

Power Supply: EVGA - SuperNOVA G3 650W 80+ Gold Certified Fully-Modular ATX Power Supply  

So, I finally did it, built my first computer! I went ahead and put everything together and Friday and held my breath as I booted for the first time..... IT WORKED! All fans buzzed on, all lights worked, I even saw something on my screen!  The computer started its POST, and was at about 45% when I had to go pee. I know, I know, how could I leave the room during that very first POST?  I had been holding my pee for a long time, antsy to get the build done.  When I came back, the PC was off, and nothing was on my screen.  Since then, I have not had ANYTHING get back to my screen.  The PC still boots up, all the fans work, all components seem to be working.... but I have never gotten back to a POST or BIOS screen.  My monitor doesn't even pick anything up.

One important note to mention:  My MOBO had a red light on it next to the BIOS 1 chip, this was representing the BIOS in use.... even though it was red I researched and saw this was normal.  I have not seen that red light come on since the first POST.

I have gone through Tom's Hardware check list more times than I can count.  I have tried single stick RAM in all slots, both sticks.  I have really tried everything that I could think of, I even started from scratch yesterday.  One of my good friends who has built several PCs in the past came over and did his routine, no luck.  I just tried resetting my CMOS, and that did not boot the PC... My MOBO does not have a case speaker, I have one of those on order now.  This is my first build so I am not too familiar with troubleshooting from here, although I am relatively tech savvy and can understand a lot of what I read.