Cannot find the metrics from the simple example in New Relic One

I am trying to implement OpenTelemetry using the exporter but cannot find the metrics in NR1.

I'm using the simple example https://github.com/newrelic/opentelemetry-exporter-go/blob/master/examples/simple/main.go

I had to modify the code a little as I'm using the EU data centre and the NewExporter itself doesn't read the environment variables the way the NewExportPipeline does.

(I've noticed in the blog posts and in the code examples there is little or no mention of the EU data centre and the need to modify code, etc.)

    metricsURL, ok := os.LookupEnv("NEW_RELIC_METRIC_URL")
    if !ok {
        fmt.Println("Missing NEW_RELIC_METRIC_URL required for New Relic OpenTelemetry Exporter")
        os.Exit(1)
    }
    tracesURL, ok := os.LookupEnv("NEW_RELIC_TRACE_URL")
    if !ok {
        fmt.Println("Missing NEW_RELIC_TRACE_URL required for New Relic OpenTelemetry Exporter")
        os.Exit(1)
    }
    exporter, err := newrelic.NewExporter(
        "Simple OpenTelemetry Service",
        apiKey,
        telemetry.ConfigBasicErrorLogger(os.Stderr),
        telemetry.ConfigBasicDebugLogger(os.Stderr),
        telemetry.ConfigBasicAuditLogger(os.Stderr),
        telemetry.ConfigSpansURLOverride(tracesURL),
        func(cfg *telemetry.Config) {
            cfg.MetricsURLOverride = metricsURL
        },
    )

The logging appears to show the example metrics and trace data being sent to NR1 successfully

2021/02/05 14:25:10.082945 {"api-key":"NRII-...","event":"harvester created","events-url-override":"","harvest-period-seconds":5,"metrics-url-override":"https://metric-api.eu.newrelic.com/metric/v1","spans-url-override":"https://trace-api.eu.newrelic.com/trace/v1","version":"0.2.0"}
2021/02/05 14:25:10.084548 {"body-length":268,"event":"data post","url":"https://metric-api.eu.newrelic.com/metric/v1"}
2021/02/05 14:25:10.084595 {"data":[{"common":{"timestamp":1612531510082,"interval.ms":0},"metrics":[{"name":"ex.com.one","type":"gauge","value":1,"timestamp":1612531510083,"attributes":{"C":"3","ex.com/lemons":10,"description":"A ValueObserver set to 1.0","instrumentation.provider":"opentelemetry","collector.name":"newrelic-opentelemetry-exporter","service.name":"Simple OpenTelemetry Service","A":"1","B":"2"}}]}],"event":"uncompressed request body","url":"https://metric-api.eu.newrelic.com/metric/v1"}
2021/02/05 14:25:10.484315 {"body":{"requestId":"e5420614-0001-b000-0000-0177725e2cc5"},"event":"data post response","status":202}
2021/02/05 14:25:10.484403 {"body-length":337,"event":"data post","url":"https://trace-api.eu.newrelic.com/trace/v1"}
2021/02/05 14:25:10.484512 {"data":[{"common":{},"spans":[{"id":"0e58001e53592a63","trace.id":"302f9b8633b71a0466005c23f6794e3a","timestamp":1612531510083,"attributes":{"name":"Sub operation...","parent.id":"6f42b4ea75989b15","duration.ms":0.002442,"service.name":"Simple OpenTelemetry Service","instrumentation.provider":"opentelemetry","collector.name":"newrelic-opentelemetry-exporter","ex.com/lemons":"five","span.kind":"internal"}},{"id":"6f42b4ea75989b15","trace.id":"302f9b8633b71a0466005c23f6794e3a","timestamp":1612531510083,"attributes":{"name":"operation","duration.ms":0.027327,"service.name":"Simple OpenTelemetry Service","ex.com/another":"yes","span.kind":"internal","instrumentation.provider":"opentelemetry","collector.name":"newrelic-opentelemetry-exporter"}}]}],"event":"uncompressed request body","url":"https://trace-api.eu.newrelic.com/trace/v1"}
2021/02/05 14:25:10.694570 {"body":{"requestId":"17bf1804-0001-b000-0000-0177725e2d95"},"event":"data post response","status":202}

I can see the "Simple OpenTelemetry Service" entity in the NR1 explorer but when I click on the Metrics explorer it tells me that "You're not collecting metric data".

newrelic / opentelemetry-exporter-go

Cannot find the metrics from the simple example in New Relic One #58