The Single List Results mode at SearchTempest is powered by Google, which supports a maximum of 32 keywords per search. (A couple of these may be used for extra settings like "dogs allowed" or "telecommuting", so you may hit the limit with a few less than 32.)
One option is to cut down the number of keywords you're using, perhaps by splitting your search into separate chunks. Alternatively, we provide a Direct Results mode, which links you directly to results pages at craigslist*. Since it doesn't use Google, it avoids this problem as well.
*We're not affiliated with craigslist.