Self test won’t stop

I bought my xc1 from an acution for super cheap so something’s probably wrong with it. I used it several times for 3 days it worked great but then after it was done charging one time when I turned it on it was on self test for 2 hours so I tried turning it off and on again and left it overnight and it’s still stuck on self test. It was on my back porch last night and the coldest it got was 45 Fahrenheit and the hottest 70 Fahrenheit. The machine is off right now.