[X-Post /r/buildapc] New built computer powers on with no video, no beep codes, even when all the RAM is removed

I've got a build with an AsRock X99 Extreme3 motherboard. I tried powering it on and all the fans/lights came on but I wasn't getting any video. The graphics card is a Geforce 980 GTX Ti, there's no integrated graphics on the mobo, it was in the PCIe 1 slot and both the graphics card itself and the molex connector on the mobo were connected to the PSU. The fans on the graphics card powered up when the machine was turned on. Based on advice I found online I've reset the CMOS and removed the mobo battery for ~15 seconds. The most concerning thing for me is that I tried disconnecting everything from the motherboard except the PSU and removing all the RAM and powering it on but even then at no point did I ever get any beep codes (though it did seem to "stutter" when powering on, i.e. the power light went on, then off, then back on, which doesn't happen when the RAM is in). Does anyone have any suggestions for what this might be?