Pregnant and not anymore more what happened help

So I am 37week pregnant still thank god🙏🏼 I am asking for my friend so she took a pregnancy test after she missed her period it came out positive and to get it confirmed she also went to the clinic to get a test they told her congratulations you are pregnant so according to her she is about 5weeks pregnant this Tuesday she went to the obgyn to get an ultrasound and the doc say sorry your not pregnant and I sAid but why not she hasn’t had her period no bleeding like if she had a miscarriage what could it be even her baby daddy new she was pregnant when he saw her and the clinic even confirmed she is pregnant