The camera doesn’t work well, it doesn’t track where my knee and foot are, even though I m doing right form for the first few attempts

Before you just assume I can’t do pushups; I weigh 160 and bench 285. I think I should be able to do quite a few. The introduction to the app was kinda cool, it provided some interesting information. Then came the part where you have to “prove how many push ups you can do,” and it grades you based on your form. I started wide grip, went chest to the ground, and all the way up of course… -8 score. So I tried again and again doing different ranges of motion, just to get the same result. I thought it was just the baggy shirt I had on, so I removed it and tried again. Same result. I then tried various other grips, different distances from my camera, and different camera angles. In the time I tried to get this to work, it only counted two out of the I don’t even know how many push ups I did, and on those two push ups, my score still went down. The only thing I learned while doing this is that your score can’t go below zero.