Negative Live Load Reactions at supports

I have a 4 span steel bridge that I am modeling. Leap steel is returning a value of 0 kip at 2 piers and negative values at the 3 pier and abutments. The supports are rollers at the two piers with 0 for reaction. Using alternate software returns a value other than 0 at these supports. Can anyone tell me why this is happening. I don't think it likely that the two piers are both values of zero. Any help would be appreciated.