Changing the error message here would be one solution or displaying the error in a modal would be another way to handle it.
Change the error message to: "Precondition failed"
Reported on google group:
As per CDS hooks specification, we have to send error 412 in case the CDS Service is unable to retrieve the necessary FHIR data to execute its decision support.
Currently sandbox shows message "Could not get a response from the CDS Service. See developer tools for more details"
Sandbox Browser console shows error 412 (Precondition failed)