Getting "No-Signal" to monitor

Hello everyone,

I'm sure this question has been asked before but on googling I couldn't find any fix for it thus far.

I'm building a new PC with these specifications:

CPU : AMD Ryzen 3 3100
Mobo: Asrock B450M Steel Legend
RAM: ADATA PC4-24000 3000MHz
Graphic Card: Sapphire Pulse RX560 4Gb / AMD Radeon HD 5450 1Gb (LP)
PSU: Thermaltake Litepower 650 Watts
O/S: Windows 10 x64

Here's my headache:
When I install the RX560 on my system, all I got is a blank screen. No BIOS, No POST, nothing... Just blank screen. However, I did notice that my hard disk light is running and towards the end, I can even hear the windows 10 startup sound. So I assume that it has to be a graphic card issue. I uninstall the RX560 and plug in an old Radeon HD 5450 that I have lying around. Lo and behold, my monitor is alive.

After much googling I saw lots of commentators suggesting an update of BIOS. Taking a look at my BIOS version, I am already at version P2.90 which is sufficient to run a Ryzen 3 but out of curiosity, I updated my BIOS to the latest 3.30 nevertheless. Pull out my HD5450 and reinserted the RX560, same issue. Blank screen. can't even see the POST screen. Took it out once again and got it installed on a friend's PC it booted up like a charm.
Somehow I got a strange feeling that it might have to do with the BIOS default setting.... The question I kept asking is what? What should I tweak?

So, I'm at wit's end trying to troubleshoot this problem. Any suggestions and help is highly appreciated.

Just a heads up:

Yes! The 8 pin power is connected to the board.
Yes! The 24 pin is also connected.
Yes! The DVI cable is connected to the graphic card and NOT the mobo which Ryzen 3 3100 does not have.
Yes! The 6 pin power is firmly attached to the RX560 whenever I plug it onto the mobo,
Yes! The fans on the RX560 run and bear in mind that it worked fine on a friend's rig.