welcome to the Atlassian Community.
The installation is maintained by your internal IT team - you reached out to Atlassian Community. Here you can meet users which voluntarily help and discuss aspects of Atlassian tools.
But members of the Community do not have access to your infrastructure as well as we do not know anything about it.
Assuming you are not asking for possible root causes of the HTTP 502-error the best you can do is reaching out to your local IT support staff.
In case you want to discuss possible root causes for the (proxy?) error further, please let Community know.
Is Confluence running behind a proxy? Was something changed shortly before the 502 error came up?
How is the setup structured exactly?
Is something from the logs showing up?
Is the base system overall okay?
Here in Community you can find many other threads related to this error but for your specific case you would need to check the system. Other you cannot determine what lead to the error status/situation.
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