Hi @Yusuf Serhat Öncül and welcome to the community!
First of all, you are aware that you have created a post on the Atlassian community and not on Atlassian support, right? With that being said, we can't actually solve anything on behalf of Atlassian, but could potentially provide with useful info to solve your problem.
What exactly is this that you can't access? Where do you login? Are the credentials correct? Are you the only one who has the problem, or are there other colleagues of yours as well?
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