gMax 1.5 MAXTEMP error

I got a used gMAX and was testing it, I have no experience with 3D printing at all, I plan to get started with this, I printed 2 samples that were no good and by the time I tried to print the third one the displayed changed the max temp to zero and displayed the MAXTEMP error. That happened 2 or 3 weeks ago, I thought it overheated so left it to cool down. Today I tried to test it again but I got the MAXTEMP from the beginning. Not sure what to do.