Authentication Error for User [elastic] When Accessing Elasticsearch from Kibana

Details of My Setup:
Version: Elasticsearch 7.9.3
Installation Type: Cluster with 3 master nodes and 3 data nodes
elasticsearch.yml Configuration:

cluster.name: xxxxx
node.name: node-xxxxx
node.master: true
node.data: true
path.data: data
bootstrap.memory_lock: true
network.host: xxxxx
network.publish_host: xxxxx
http.port: xxxxx
transport.tcp.port: xxxxx
discovery.seed_hosts: ["IP1:PORTA","IP2:PORTA","IP3:PORTA"]
cluster.initial_master_nodes: ["node-xxxxx","node-xxxxx","node-xxxxx"]
action.auto_create_index: true
action.destructive_requires_name: true
xpack.security.enabled: true
xpack.security.transport.ssl.enabled: true
xpack.security.transport.ssl.verification_mode: certificate
xpack.security.transport.ssl.keystore.path: /xxxxxx/elasticsearch/config/elastic-certificates.p12
xpack.security.transport.ssl.truststore.path: /xxxxxx/elasticsearch/config/elastic-stack-ca.p12

kibana.yml Configuration:

server.port: xxxx
server.host: 0.0.0.0
elasticsearch.hosts: ["IP1:PORTB","IP2:PORTB","IP3:PORTB"]
i18n.locale: en

I have already tried modifying the Elasticsearch password, and curl commands are working correctly. The Elasticsearch cluster is also functioning normally. However, when I start Kibana, I still encounter the same authentication error.
Could you please provide any additional steps or configurations that might help resolve this issue?

Best regards.