tb-350 btc no boot with more than one gpu

[etqg]

Hi, trying to set up a tb350 btc with 2 x 1050ti and 2 x 750ti, but it won't boot with more than one graphics card installed.. I did have it working with 2 at one stage but now I can't figure out how I did that. I'm sure there is something simple I am missing.. help !