two monitors on display

I have just installed a raedon rx 650 graphics card .  it has a dvi and hdmi port at the back of the card.   I have tried to hook up two monitors to the card using a hdmi monitor plug and dvi adapter on the other monitor.  computer doesn't detect either monitor.  when I disconnect one of the monitors, the other one works and is detected.    I have also tried to use a hdmi splitter / switcher but that hasn't worked.  same deal if I pull out one of the leads. the other monitor works.   question:   how do I connect two monitors to the card I have and can it be done?     have also tried to use the motherboard onboard graphics card for one of the monitors, but that doesn't work either.   any answers?