Getting Alert test sending failed, [null] in ds.

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i am using dd version 3.2.1 and deployed the same as K8 pods. Post configuring the alert Instance, while submitting test Send getting the error - Alert test sending failed, [null] . From logs belwo are hte detailed error -
[ERROR] 2024-05-07 20:38:11.226 +0800 o.a.d.a.s.i.AlertPluginInstanceServiceImpl:[358] - Send alert: AlertTestSendRequest(pluginDefineId=7, pluginInstanceParams=[{"props":{"disabled":null,"type":null,"maxlength":null,"minlength":null,"clearable":null,"prefixIcon":null,"suffixIcon":null,"rows":null,"autosize":null,"autocomplete":null,"name":null,"readonly":null,"max":null,"min":null,"step":null,"resize":null,"autofocus":null,"form":null,"label":null,"tabindex":null,"validateEvent":null,"showPassword":null,"placeholder":"input WebHook Url","size":"small"},"field":"webHook","name":"WebHook","type":"input","title":"$t('webhook')","value":"https://hooks.slack.com/services/T0CN2XXP/BUSS6CNBS/XXXXXXXXXXXXXXXXXX","validate":[{"required":true,"type":"string","trigger":"blur","min":null,"max":null}],"emit":null},{"props":{"disabled":null,"type":null,"maxlength":null,"minlength":null,"clearable":null,"prefixIcon":null,"suffixIcon":null,"rows":null,"autosize":null,"autocomplete":null,"name":null,"readonly":null,"max":null,"min":null,"step":null,"resize":null,"autofocus":null,"form":null,"label":null,"tabindex":null,"validateEvent":null,"showPassword":null,"placeholder":"input the bot username","size":"small"},"field":"username","name":"Username","type":"input","title":"$t('Username')","value":"SampleUser","validate":[{"required":true,"type":"string","trigger":"blur","min":null,"max":null}],"emit":null}]) to: Host(ip=dolphinscheduler-alert-668df89b7d-9vx8v, port=50052) failed
Caused by: org.apache.dolphinscheduler.extract.base.exception.RemotingException: connect to : Host(ip=dolphinscheduler-alert-668df89b7d-9vx8v, port=50052) fail
at org.apache.dolphinscheduler.extract.base.NettyRemotingClient.sendSync(NettyRemotingClient.java:194)
at org.apache.dolphinscheduler.extract.base.client.SyncClientMethodInvoker.invoke(SyncClientMethodInvoker.java:46)
at org.apache.dolphinscheduler.extract.base.client.ClientInvocationHandler.invoke(ClientInvocationHandler.java:55)
... 80 common frames omitted

[ERROR] 2024-05-07 20:38:11.227 +0800 o.a.d.a.e.ApiExceptionHandler:[40] - org.apache.dolphinscheduler.api.controller.AlertPluginInstanceController#testSendAlertPluginInstance[2 args] Meet a ServiceException: Alert test sending failed, [null]
172.16.45.81 - - [07/May/2024:12:38:11 +0000] "POST /dolphinscheduler/alert-plugin-instances/test-send HTTP/1.1" 200 104 13ms

Coudl anyone please assist on this? belwo is the yaml section for alert i have used. Ay additional configurations to be done for this?
alert:

-- Enable or disable the Alert-Server component

enabled: true

-- Number of desired pods. This is a pointer to distinguish between explicit zero and not specified. Defaults to 1.

replicas: 1

-- The deployment strategy to use to replace existing pods with new ones.

strategy:
# -- Type of deployment. Can be "Recreate" or "RollingUpdate"
type: "RollingUpdate"
rollingUpdate:
# -- The maximum number of pods that can be scheduled above the desired number of pods
maxSurge: "25%"
# -- The maximum number of pods that can be unavailable during the update
maxUnavailable: "25%"

-- You can use annotations to attach arbitrary non-identifying metadata to objects.

Clients such as tools and libraries can retrieve this metadata.

annotations: {}

-- Affinity is a group of affinity scheduling rules. If specified, the pod's scheduling constraints.

More info: node-affinity

affinity: {}

-- NodeSelector is a selector which must be true for the pod to fit on a node.

Selector which must match a node's labels for the pod to be scheduled on that node.

More info: assign-pod-node

nodeSelector: {}

-- Tolerations are appended (excluding duplicates) to pods running with this RuntimeClass during admission,

effectively unioning the set of nodes tolerated by the pod and the RuntimeClass.

tolerations: []

-- Compute Resources required by this container.

More info: manage-resources-containers

resources: {}

resources:

limits:

memory: "2Gi"

cpu: "1"

requests:

memory: "1Gi"

cpu: "500m"

Thank you