Question second monitor 'no signal detected'

[LaMii]

I built a new pc with my old graphics card and it had a problem where i had to restart my pc everytime i wanted my second monitor to turn on.
Now that it's in my new pc only my main monitor can turn on and my second monitor is saying 'no signal detected!'.
ive tried many basic things already, such as, checking if its pluggedin properly, faulty cable, win+p to extend monitor, detect monitor in display settings and nvidia, updating gpu drivers, roll back drivers; none of them worked for me.
sometimes the second monitor would turn on if i unplug my main monitor, but the second monitor just stays at a black screen until i replug my main monitor then y second monitor returns to being 'no signal detected'.
PC specs:
Cpu = amd ryzen 5 2600x
ram = hyper x 8gb 2666hz
gpu = nvidia gtx 1070 8gb
m/b = b450 pro4
psu = 750w
os = windows 10 home 64bit

 

[LaMii]

make and model of the psu?
so the issue is with the port or the monitor?
try switch 1st and 2nd monitor?

psu = thermaltake smart pro rgb 750w
and i can't switch monitors as aoc doesnt have a dvi and the benq doesnt have a dp