How to force flash?

irvcobb

I just moved to a T3i from a Panasonic FZ150. A Yongnuo 560 strobe and a cheap wireless trigger moved with me. The strobe must be set up manually, no auto. My experience thus far is that the camera seems to fail to fire the strobe at seemingly random times; I think it's related to exposure. I am confident that the problem is not the trigger or the strobe, so is there a way to set the camera up so that it always fires the flash?