Google Cloud Ops Agent does not save logs when time_key is set

Question

Applies to configuration: Logging processors

This setup works:

/etc/google-cloud-ops-agent/config.yaml

logging:
  receivers:
    app:
      type: files
      include_paths: [/www/logs/app-*.log]
  processors:
    monolog:
      type: parse_regex
      field: message
      regex: "^\[(?<time>[^\]]+)\]\s+(?<environment>\w+)\.(?<severity>\w+):\s+(?<msg>.*?)(?<context>{.*})?\s*$"
  service:
    pipelines:
      default_pipeline:
        receivers: [app]
        processors: [monolog]

I am trying to configure time_key, but the logs do not show up in the log viewer. I call the API whether the logs are being processed, whether they are read and sent. They come out but are not in the log viewer.

logging:
  receivers:
    app:
      type: files
      include_paths: [/www/logs/app-*.log]
  processors:
    monolog:
      type: parse_regex
      field: message
      regex: "^\[(?<time>[^\]]+)\]\s+(?<environment>\w+)\.(?<severity>\w+):\s+(?<msg>.*?)(?<context>{.*})?\s*$"
      time_key:    time
      time_format: "%Y-%m-%d %H:%M:%S"
  service:
    pipelines:
      default_pipeline:
        receivers: [app]
        processors: [monolog]

Log structure:

[2021-10-06 12:12:08] production.EMERGENCY: Testing {"abc":"xyz"}

Parsed (first code example):

{
  jsonPayload: {
    context: "{"abc":"xyz"}"
    environment: "production"
    msg: "Testing "
    severity: "EMERGENCY"
    time: "2021-10-06 12:12:08"
  }
}

API call to check logs processed:

curl -s localhost:2020/api/v1/metrics | jq

From strptime(3) also tried to use "%F %H:%M:%S"

What am I doing wrong?