Hi @Visnu P Kumarr and welcome to the community,
If you are on a server jira, you have to contact your administrator and let him know of your problem and message you are receiving. There could be alot of things as to why you can't login.
If you are on cloud, you have to let us know which plan you are on, and if you are eligible for Atlassian's support.
In any case, a screenshot of the message and the url you are trying to login would be very helpful.
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