Troubleshooting report viewer launcher Client found response content type of 'text/html; charset=utf-8', but expected 'text/xml'. The request failed with the error message

In this case, notice the error "

The report server cannot open a connection to the report server database. A connection to the database is required for all requests and processing. (rsReportServerDatabaseUnavailable)

It took me a while to realize/remember that the MT application I was running locally uses the credentials in web.config for the report viewer:

    <add key="ReportServerAccessAccountUsername" value="ReportServiceAccount"/>

    <add key="ReportServerAccessAccountPassword" value="Tr@p3z3"/>

    <add key="ReportServerAccessAccountDomain" value="AZ-Dev5"/>