If the dishwasher won't run at all and the clean light is flashing 7 times it is because the control thinks the heater is not working.
You can clear the error by running a diagnostic test but if the heater isn't working then the lights will flash again until the problem is fixed.
The image below will show you how to enter and run a diagnostic cycle.
This should clear the error and allow you to use the dishwasher. Try to notice if there is any steam at the end of the cycle or if the dishes are hot to touch.
If there is no steam and the dishes are not hot then it is likely the heater is not working. The problem can be the element, hi limit thermostat or control.
I hope this helps. You can reply to the question with any additional details. Your reply will trigger an email to me and I will try to assist you further.