Samsung Fridge/freezer not working Panels reads 36/4degrees butit is warm inside

I picked up this Fridge in hopes of getting it working, my son is a apartment maintaince manager and he is visiting for a few days and we are trying to trouble shoot the fridge while he is here.
We plugged it in and he pushed the buttons for a diagnostic after taking off the panel and checking for connection the temp display started to drop evenly for over an hour but when we opened it it was not cold?-History
Bought fridge from a rental agency that had called a repair guy and he said it was fixed then it quit working again shortly after. I suspected the freezing up issue, but since I have had it it hasn’t ever gotten cold–
There is airfow, the compressor appears to be working and the lines and everythign look to be in good order.
Now need to now how or where to start to troubleshoot–

Thanks, Kim