Power supply not working
I would expect the root cause to simply be the power supply itself.

5&nbsp;Ω is a reasonable resistance for a 12&nbsp;V / 30 W heater. It seems strange that you are not seeing continuity in the heated bed as this should also have a low resistance (since it's a heater as well). This might be worth investigating further, but I think it's more likely the power supply itself is the cause (and you simply made a measurement error).