Sun Impatiens is really a misnomer. Sun Impatiens will take more sun than the regular ones but they still like to be shaded during the heat of the day or they will wilt. With the hot weather this last that woulkd be more the case than ever.

Maybe too you didn't give them enough water

Last year the SunPatiens done very well.This year they didn't bloom much at all.They had partial shade & enough water.
Rose

Thanks for the comments. I too, decided that they really didn't like all that hot sun, so I moved them to a more shaded spot. However, I can't say they really thrived anywhere. I tried pruning them, with the intention of rooting the cuttings. I did get one plant that way, but it isn't growing much; just sitting there. Live & learn.

I have seen these grown in Texas, Illinois, California, Michigan and Pennsylvania, and they have always looked great. What kind of soil do you have them planted in?

"Consumer Care
SunPatiens do best in raised beds where the soil is well aerated and rich in organic matter. Incorporate slow release
fertilizer prior to planting and water sufficiently to establish the bed. Once established, SunPatiens are fairly drought tolerant. In heavier soils, consider using Vigorous types as they are better at tolerating less than ideal conditions. SunPatiens tolerate lower soil temperatures (55�F/13C) and can be planted earlier than many other heat-loving annuals, like vinca. This is a key advantage for landscapers who need plants to perform and look good over a long growing season.