While rendering the dashboard we get, Access denied error or service could not be contact error in rare cases.
In this case we have to ask the customer to ensure the following cases,
# Whether the Dashboard Service or API is running stated
# Check the machine key in all config files are same.
We have done the above validation in our application level. We can add the separate utility or separate page in dashboard server for validating the above cases. Please check and done which option is best for validation.