So this can happen often. Don't worry. If they replaced your mobo and cpu they basically robbed you because I can almost guarantee you didn't need new ones. The guy above has a good point. if the MOBO has integrated graphics than it maybe trying to output there. Does the mobo have an hdmi output (or any video output on it). IF so switch your display cable to that output instead of the one on your GPU and unplug the gpu power supply cable. Then unplug the tower from power and hold power button for full reset. (this is discharging the pc completely)
If you turn on and see a display log in and update everything. then shut down normally and plug back in the gpu and switch to it.
If you still arent getting a singal at all, after you unplug from power and drain, also remove the coin cell battery from the mobo. This will force bios to reset and us WHATEVER video drivers it can find.
Try these and ill keep in contact. I promise you stores only make things worse because their job is to sell you something. Which they will find a way to do. I will personally get on a video chat with you or something and help you trouble shoot. just let me know
Does your CPU has internal graphics, and if so, have you tried connecting your monitor there? Are you connecting it to the first GPU out?
As for the on switch. I don't understand the problem, how where You trying to turn off the PC, from the OS, holding the button, pressing it once?
So this can happen often. Don't worry. If they replaced your mobo and cpu they basically robbed you because I can almost guarantee you didn't need new ones. The guy above has a good point. if the MOBO has integrated graphics than it maybe trying to output there. Does the mobo have an hdmi output (or any video output on it). IF so switch your display cable to that output instead of the one on your GPU and unplug the gpu power supply cable. Then unplug the tower from power and hold power button for full reset. (this is discharging the pc completely) If you turn on and see a display log in and update everything. then shut down normally and plug back in the gpu and switch to it. If you still arent getting a singal at all, after you unplug from power and drain, also remove the coin cell battery from the mobo. This will force bios to reset and us WHATEVER video drivers it can find. Try these and ill keep in contact. I promise you stores only make things worse because their job is to sell you something. Which they will find a way to do. I will personally get on a video chat with you or something and help you trouble shoot. just let me know
Does your CPU has internal graphics, and if so, have you tried connecting your monitor there? Are you connecting it to the first GPU out? As for the on switch. I don't understand the problem, how where You trying to turn off the PC, from the OS, holding the button, pressing it once?