Where are you plugging it into the back, which color is the port? See page 10 for the available connectors and what they represent. It should be plugged into the green one, numbered 8 on that diagram. R10 user guide 
Bought a new Aurora R10, AMD5900 with 32G of ram and 3080 Ti. Was excited to get this new desktop. On the 19th of December I was updating drivers and what not when all of the sudden screen went black and was not getting any signal. Contacted Dell services and had tech come out to house. Ended up replacing the motherboard 3 times and the video card one time. Almost everything is working now. I have stand alone Logitech Z533 speakers that were working just fine out of the rear 3.5mm jack. Tech left once screen and what not was on and working. Go to play something on YouTube and no sound. Run all the diagnostics I can and still nothing. Move the jack to the front access port and sound plays just fine. Does anyone know what I am dealing with here?
Aurora R10, rear audio jack no longer working