Can you post the make and model number please.
Ok this wont be down to the boiler as usually a dishwasher is plumbed up to cold water supply anyway.
But these have a heater in there anyway so it will heat its own water up. If its not heating up then its usually either a faulty heater or control board.
To check yourself you need to pull the dishwasher out and remove the top and the right hand side panel. From there you will see the heater at the bottom. Is a longer silver cylinder on these.
Check the wires there as these can burn out. If ok then you will need a multimeter and check the heater. If ok then on certain models theres a thermostat screwed to the tub near the heater. You need to check this aswell.
But if all thats fine then its possibley a faulty control unit. Remove the control panel and take the control board off. See if theres a burn mark or dry joint on there. If so try and resolder it if you can see how it goes from there.
But if its not drying or heating then it wont be nothing to do with your new boiler as these dishwashers heat there own water up.