2 Step no cut dark paper problem

I’m trying to do my first successful transfer but I have already had problems. I married the image successfully but when I went to transfer it onto a shirt the entire image came up after pressing. It is a cold peel and I thought I let it cool enough, but I’m not sure what happened. Could this be a pressure problem, material problem, not being cold enough, or bad print? I don’t want to waste expensive paper without more direction. Thank you