You won't get system-admin rights - that's restricted to Atlassian support.
To get confluence-admin granted in the case where your existing admins have left without granting it to you, contact OnDemand support at support.atlassian.com
Do you use templates with Confluence? Take part in a remote 1-hr workshop. You'll receive USD $100 for your time! We're looking for people to participate in a remote 1-hr workshop...
Connect with like-minded Atlassian users at free events near you!Find a group
Connect with like-minded Atlassian users at free events near you!
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You're one step closer to meeting fellow Atlassian users at your local meet up. Learn more about AUGs