I am looking at migrating a confluence server to cloud, however trying to select the cloud account to migrate to is failing to load.
After I click 'Choose cloud site', the browser attempts to open migration.atlassian.com but receive 'This site can't be reached'

If I try and login to atlassian.com, I get 'Something went wrong while attempting to validate your credentials.'
The browser console is filled iwth access denied messages:

I am traversing an enterprise proxy to get out to the internet. From a private connection, I can login but naturally I cant access our private confluence server from here to do the migration.
Ordinarily if this was our proxy blocking, I would see proxy related messages in here. The fact its giving err_access_denied suggests atlassian is blocking our proxies public facing IPs?