Getting 15K error messages an hour about HTTP 406

A production Apollo server with these plug ins:
ApolloServerPluginLandingPageDisabled
ApolloServerPluginUsageReportingDisabled
ApolloServerPluginSchemaReportingDisabled
ApolloServerPluginInlineTraceDisabled

Is throwing 15K error messages with this message:
"
Error sending report to Apollo servers: HTTP status 406, Please check your API key in the Engine configuration
"

What else should be done to stop those errors?