The computer started well and worked fast and quietly, but the two DP ports and 4 USB3 ports (2 in the back and in the front)  are not working. Emailed Tekrefurbs customer service. Two weeks now, but no response yet. I inspected the back of the PC and found that the cover of the ports was not even. Pushed down the area around the display ports , and the display ports started to work now but still not stable. Upgrade it from 1 star (mainly for the frustration of no responses) to 4 stars (overall a great PC with some minor issues to fix). Update: press F12, get into bios, uncheck and recheck the USB setting, Now, all USB3 ports are working! Additional update; Working well in the past ten months. If your USB3 port still stop work even you change the setting in BIOS, you can fix it by unchecking a box in the device manager for the USB3 port (do not let the PC turn off USB to save power). Refer to the attached picture.