Prometheus firing rules does not trigger alertmanager

I have a Prometheus 2.47.2 configured as such:

global:
  scrape_interval: 1m
  scrape_timeout: 10s
  evaluation_interval: 1m
alerting:
  alertmanagers:
  - follow_redirects: true
    enable_http2: true
    scheme: http
    path_prefix: /barracuda-monitoring
    timeout: 10s
    api_version: v2
    static_configs:
    - targets:
      - localhost:3041
rule_files:
- ...
scrape_configs:
- ...

And an AlertManager configured as such:

global:
  resolve_timeout: 5m
  http_config:
    follow_redirects: true
    enable_http2: true
  smtp_hello: localhost
  smtp_require_tls: true
  pagerduty_url: https://events.pagerduty.com/v2/enqueue
  opsgenie_api_url: https://api.opsgenie.com/
  wechat_api_url: https://qyapi.weixin.qq.com/cgi-bin/
  victorops_api_url: https://alert.victorops.com/integrations/generic/20131114/alert/
  telegram_api_url: https://api.telegram.org
  webex_api_url: https://webexapis.com/v1/messages
route:
  receiver: local-irc
  group_by:
  - alertname
  continue: false
  routes:
  - receiver: local-irc
    continue: false
  group_wait: 30s
  group_interval: 5m
  repeat_interval: 4h
receivers:
- name: local-irc
  webhook_configs:
  - send_resolved: true
    http_config:
      follow_redirects: true
      enable_http2: true
    url: http://localhost:3050/barracuda-monitoring
    url_file: ""
    max_alerts: 0
templates: []

However when Prometheus rules are firing, I do not get the notifications.

While I get the notifications when:

  • I send a direct request to AlertManager
  • I trigger a test alert from Grafana
  • I have a firing alert on Grafana

Am I missing something?

Thanks in advance for your help.