Multiple channels configured in alertmanager won't work?

[Ranchester]

I want to connect this plugin to multiple RocketChat channels, by alert severity.

I tried:

route:
   repeat_interval: 4h
   group_interval: 10m
   receiver: warning_alerts

   routes:
   - match:
          severity: critical
    receiver: critical_alerts

receivers:
   - name: 'warning_alerts'
      webhook_configs:
         - send_resolved: true
            url: 'MYCHATURL/hooks/MYTOKEN
   - name: 'critical_alerts'
      webhook_configs:
         - send_resolved: true
            url: 'MYCHATURL/hooks/MYTOKEN2

This does not seem to work? Should it work?

br. Ranchester