Oh, I see. There are some caveats that I failed to mention with the program :)
Don't search for shiny spreads (or if you are, then you're going to have to modify the search away from flawless). I'll tell you how to do it for normal spreads first
Desired Nature: Whatever it is, enter here
Search for Shiny? N
Input hidden power base: Leave this blank for spreads w/o hidden power
Exact IVs: N - important..always no here
yadda yadda yadda the rest
It won't fail you this time, guaranteed.
Now if you want shiny spreads...do the same thing (entering in ID/SID combo) but when you search for IVs, do it low. You don't want all shiny spreads, but you can't expect flawless either. Just search 25+ for example on important stats and skim through the results :)