Our JIRA Administrators are unable to view either the Custom Fields page or the Fields page of any project. The browser shows the following error:
Proxy Error
The proxy server received an invalid response from an upstream server.
The proxy server could not handle the request GET /plugins/servlet/project-config/PCWORKS/fields.
Reason: Error reading from remote server
Prior to this error, we migrated the application to our Data Center and then I did a background re-index that took almost a week to complete. I suspect that because background re-index allows users to work in JIRA, changes to the configuration, new/modified custom fields, among others may have caused for the error to occur.