OTLP Collector to Graphana Cloud Tempo - 401

Question

I have a OTLP instance running that collects traces successfully over grcp. But when I try to uplad the traces to my grafana cloud tempo instance I get this error:

grafana-collector-1 | 2023-12-31T23:51:39.371Z error exporterhelper/retry_sender.go:126 Exporting failed. The error is not retryable. Dropping data. {"kind": "exporter", "data_type": "traces", "name": "otlp", "error": "Permanent error: rpc error: code = Unauthenticated desc = unexpected HTTP status code received from server: 401 (Unauthorized); transport: received unexpected content-type "application/json"", "dropped_items": 1}

My Tempo instance runs at: https://tempo-prod-10-prod-eu-west-2.grafana.net/tempo

So I have created such a configuration for OTLP Collector:

extensions:
  basicauth/otlp:
    client_auth:
      username: <User Id>
      password: <API Access Token>

exporters:
  otlp:
    auth:
      authenticator: basicauth/otlp
    endpoint: tempo-us-central1.grafana.net:443
    headers:
       authorization: Basic <API Access Base64>

I have created with: echo -n '<User Id>:<API Access Token>' | base64

Can anyone help I'm new to OpenTelemetry