Alert Silences set in the administrator console are not set against the correct instance when a user workload alertmanger are deployed. 

replication steps: 

1: deploy UWL monitoring 

apiVersion: v1
kind: ConfigMap
metadata:
  name: cluster-monitoring-config
  namespace: openshift-monitoring
data:
  config.yaml: |
    enableUserWorkload: true 

2: deploy UWL alertmanager: 

apiVersion: v1
kind: ConfigMap
metadata:
  name: user-workload-monitoring-config
  namespace: openshift-user-workload-monitoring
data:
  config.yaml: |
    alertmanager:
      enabled: true 
      enableAlertmanagerConfig: true 

Deploy sample application: 
https://access.redhat.com/articles/7024800

Query to confirm the alert is firing on the UWL instance: 

$ oc exec n openshift-user-workload-monitoring alertmanager-user-workload-0 – amtool alert query  -alertmanager.url http://localhost:9093 
Alertname     Starts At                Summary  State   
VersionAlert  2025-02-24 20:18:17 UTC           active  

Set a silence in the GUI: label = alertname, value = VersionAlert

now query the UWL instance for the silence: 

$ oc exec -n openshift-user-workload-monitoring alertmanager-user-workload-0 – amtool silence query --alertmanager.url http://localhost:9093 
ID  Matchers  Ends At  Created By  Comment  

its not there! 
now query the core instance to find the silence: 

$ oc -n openshift-monitoring exec -ti alertmanager-main-0 -c alertmanager – amtool silence query --alertmanager.url http://localhost:9093 
ID                                    Matchers                           Ends At                  Created By  Comment  
8d1c9189-74f9-40b5-acbb-c5dde5f916e5  alertname="VersionAlert"           2025-02-24 22:22:39 UTC  kube:admin  test