Kibana stopped working after update

After the update kibana is not working.
http://localhost:5601/
response - "Kibana server is not ready yet"

$ journalctl -u kibana.service
Sep 29 12:03:21 Notebook systemd[1]: Stopping Kibana...
Sep 29 12:03:55 Notebook systemd[1]: kibana.service: Succeeded.
Sep 29 12:03:55 Notebook systemd[1]: Stopped Kibana.
Sep 29 12:03:55 Notebook systemd[1]: Started Kibana.

ive deleted kibana managment index and its still now working
curl -XDELETE http://localhost:9200/*kibana* -u username:password

Welcome to our community! :smiley:

What do your Kibana logs show?

The journalctl -u kibana.service

Sep 29 11:17:08 HP-Pavilion-Notebook systemd[1]: Started Kibana.
Sep 29 11:41:11 HP-Pavilion-Notebook systemd[1]: Stopping Kibana...
Sep 29 11:41:49 HP-Pavilion-Notebook systemd[1]: kibana.service: Succeeded.
Sep 29 11:41:49 HP-Pavilion-Notebook systemd[1]: Stopped Kibana.
Sep 29 11:41:49 HP-Pavilion-Notebook systemd[1]: Started Kibana.
Sep 29 11:44:26 HP-Pavilion-Notebook systemd[1]: Stopping Kibana...
Sep 29 11:44:58 HP-Pavilion-Notebook systemd[1]: kibana.service: Succeeded.
Sep 29 11:44:58 HP-Pavilion-Notebook systemd[1]: Stopped Kibana.
Sep 29 11:44:58 HP-Pavilion-Notebook systemd[1]: Started Kibana.
Sep 29 11:53:47 HP-Pavilion-Notebook systemd[1]: Stopping Kibana...
Sep 29 11:54:20 HP-Pavilion-Notebook systemd[1]: kibana.service: Succeeded.
Sep 29 11:54:20 HP-Pavilion-Notebook systemd[1]: Stopped Kibana.
Sep 29 11:54:20 HP-Pavilion-Notebook systemd[1]: Started Kibana.
Sep 29 12:03:21 HP-Pavilion-Notebook systemd[1]: Stopping Kibana...
Sep 29 12:03:55 HP-Pavilion-Notebook systemd[1]: kibana.service: Succeeded.
Sep 29 12:03:55 HP-Pavilion-Notebook systemd[1]: Stopped Kibana.
Sep 29 12:03:55 HP-Pavilion-Notebook systemd[1]: Started Kibana.

systemctl status kibana

ibana.service - Kibana
     Loaded: loaded (/etc/systemd/system/kibana.service; disabled; vendor prese>
     Active: active (running) since Wed 2021-09-29 12:03:55 IST; 1h 19min ago
       Docs: https://www.elastic.co
   Main PID: 15332 (node)
      Tasks: 18 (limit: 9346)
     Memory: 321.2M
     CGroup: /system.slice/kibana.service
             ├─15332 /usr/share/kibana/bin/../node/bin/node /usr/share/kibana/b>
             └─15348 /usr/share/kibana/node/bin/node --preserve-symlinks-main ->

Sep 29 12:03:55 HP-Pavilion-Notebook systemd[1]: Stopped Kibana.
Sep 29 12:03:55 HP-Pavilion-Notebook systemd[1]: Started Kibana.

It'd be better if you could check /var/log/kibana/kibana.log.

{"type":"log","@timestamp":"2021-09-29T12:04:37+05:30","tags":["info","plugins","reporting","config"],"pid":15348,"message":"Chromium sandbox provides an additional layer of protection, and is supported for Linux Ubuntu 20.04 OS. Automatically enabling Chromium sandbox."}
{"type":"log","@timestamp":"2021-09-29T12:04:37+05:30","tags":["warning","plugins","encryptedSavedObjects"],"pid":15348,"message":"Saved objects encryption key is not set. This will severely limit Kibana functionality. Please set xpack.encryptedSavedObjects.encryptionKey in the kibana.yml or use the bin/kibana-encryption-keys command."}
{"type":"log","@timestamp":"2021-09-29T12:04:37+05:30","tags":["warning","plugins","actions"],"pid":15348,"message":"APIs are disabled because the Encrypted Saved Objects plugin is missing encryption key. Please set xpack.encryptedSavedObjects.encryptionKey in the kibana.yml or use the bin/kibana-encryption-keys command."}
{"type":"log","@timestamp":"2021-09-29T12:04:37+05:30","tags":["warning","plugins","alerting"],"pid":15348,"message":"APIs are disabled because the Encrypted Saved Objects plugin is missing encryption key. Please set xpack.encryptedSavedObjects.encryptionKey in the kibana.yml or use the bin/kibana-encryption-keys command."}
{"type":"log","@timestamp":"2021-09-29T12:04:37+05:30","tags":["info","plugins","ruleRegistry"],"pid":15348,"message":"Write is disabled; not installing common resources shared between all indices"}
{"type":"log","@timestamp":"2021-09-29T12:04:38+05:30","tags":["info","plugins","ruleRegistry"],"pid":15348,"message":"Write is disabled; not installing resources for index .alerts-observability.uptime.alerts"}
{"type":"log","@timestamp":"2021-09-29T12:04:38+05:30","tags":["info","plugins","ruleRegistry"],"pid":15348,"message":"Write is disabled; not installing resources for index .alerts-observability.logs.alerts"}
{"type":"log","@timestamp":"2021-09-29T12:04:38+05:30","tags":["info","plugins","ruleRegistry"],"pid":15348,"message":"Write is disabled; not installing resources for index .alerts-observability.metrics.alerts"}
{"type":"log","@timestamp":"2021-09-29T12:04:38+05:30","tags":["info","plugins","ruleRegistry"],"pid":15348,"message":"Write is disabled; not installing resources for index .alerts-observability.apm.alerts"}
{"type":"log","@timestamp":"2021-09-29T12:04:38+05:30","tags":["info","savedobjects-service"],"pid":15348,"message":"Waiting until all Elasticsearch nodes are compatible with Kibana before starting saved objects migrations..."}
{"type":"log","@timestamp":"2021-09-29T12:04:38+05:30","tags":["error","savedobjects-service"],"pid":15348,"message":"This version of Kibana (v7.15.0) is incompatible with the following Elasticsearch nodes in your cluster: v7.14.1 @ localhost/127.0.0.1:9200 (127.0.0.1)"}

kibana is updated from 7.14 to 7.15, Elasticsearch version is 7.14

You should check that out and upgrade Elasticsearch.