The manual warns against using extension cords. The X50s draws significant current during rapid heating cycles. It is imperative to plug the unit directly into a grounded wall outlet. If your lab has 230V requirements, ensure the voltage selector on the back is configured correctly—a step detailed in the "Getting Started" section of the manual.
If you have lost the manual, here is the exact workflow to program a 3-step PCR. eppendorf mastercycler x50s manual