You'll need to replace your thermal fuse on the top of your boiler if your boiler will not heat and there is a lack of continuity.
This is a replacement thermal fuse, sometimes called a thermal cut-off or high limit, for an Isomac home espresso machine. These are an upgrade from the original fuses, simply because they are at the correct temperature rating (157 degrees Celsius). The Isomac machines come with a too high rated fuse (184 degrees Celsius) and as a result, the heating element will blow in many cases.
The thermal fuse on many of the Isomac espresso machines is located above the heating element. When you're replacing the thermal cut-off please remember to replace the insulated sleeve as it needs to be reused.