Allway Tools P707 4x8 Greenhouse for Gardening

I hate to write a book, but I decided to be the guinea pig since there were no reviews at the time of purchasing this. Here's my experience.I bought this little "greenhouse" because it was cheap (around $3 at the time) and small in size (perfect for me since I don't have a lot of indoor space). Keep in mind that this is NOT the first time I've grown anything nor the first time I've started seedlings indoors. However, before, I used the trays and soil.Fast forward a few days later after setting everything up and I only had four (out of the 10) seeds to sprout! I removed them from the dome once they were actually touching the top of it (as per the instructions) and put them into a seedling tray. They seemed to be doing well for the next couple days but then, all of a sudden, they all started to die (three first and then the last finally died a few days later).I'm not gardening pro but I do well with growing and have never had anything die on me, so it was a bit disheartening. I only have two windows in my home and neither with an accessible sill, so I had this sitting by the glass sliding door in my bedroom (the same place I start out all my other seedlings). I also had it sitting on a heating mat (again, what I always use without issue).I'm not sure where or IF I went wrong with this! Everything was fine but then the few that did sprout just died on me. The other six never sprouted at all, which is very strange. I decided to try all of the same things I had planted in these outside and guess what? They're all growing wonderfully and are flourishing.I will add that I found this very easy to set up and it comes with easy-to-follow directions that even newbies can follow, it just seems to kill everything! :( I had 10 DIFFERENT seeds planted - two seeds per pellet (the instructions say you can use 1-2 seeds per pellet). The pellets expand well and within a couple minutes after watering them.I did notice that there was a LOT of condensation that built up inside the dome and had a bit of a funny smell to it. Maybe this was the issue? Maybe it was the heat mat that caused this extra moisture buildup and ruined the seeds? Who knows. I probably won't buy this again to see, though. I'm really disappointed.