Hello @Kunal Sambharwal ! Welcome to the Atlassian Community!
The link you provided is an internal link that we can't see. Can you show a screenshot?
Based on the error message, you probably moved to a version of Jira that doesn't support your database. You may have to back out of the Jira upgrade, upgrade your database to a supported version, and then upgrade Jira.
The page showing supported versions for 8.20 is here: https://confluence.atlassian.com/adminjiraserver/jira-applications-installation-requirements-938846826.html
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