The MSI z97 mate I looked up has PCIe slots and PCI slots. The cards you noted require power connections but you didn't write about that or tell about the PSU.
Tell more.
PC suddenly started to send no signal to monitor. Black screen appears, Graphics card is Asus R9 285 DCII, has a backplate so PCB is straigh still. Mainboard is MSI Z97 PC Mate, processor i5-4460. Mainboard has VGA, DVI and HDMI outputs, tried to plug DVI to monitor using i5-4460's HD Graphics 4600 and it worked successfully. When I plug it to graphics card and start PC, a warning shows on monitor ''No Signal''(It has a signal at start and something triggers that signal) and it goes black again. You can shut down the computer with 1 power button click without holding after if its plugged to graphics card and switching outputs makes no diffrence. My graphics card R9 285 has led indicators on 6-pin molex power supplies and both flashing white as usual. GPU always worked under 90 celcius both summer and winter. Graphics card warranty still continues and warranty seal (A screw of DirectCU II cooler touching GPU or thermal paste is sealed) is not touched. Mainboard has 16x and 8x PCI slots, both is not working or GPU bye bye.
I have another Sapphire HD 7870 for testing if PCI slot is corrupted but that one had cooked a lot and not sure if it's working or not but it didn't send information to screen but triggers ''No Signal''.
HD 7870 always had the fans working at %100 after boot
R9 285 fans never spinned. (It doesn't spin if it's idle after boot but never checked if it were turning or not before boot ever. Works on max of 50 celcius when outside is ~30 while fans are not spinning)
I can send photos if anyone is interested.

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