This error seems to be the same one described on this topic: https://answers.atlassian.com/questions/24653287/how-to-link-a-service-desk-to-a-confluence-space
Can you confirm you have enabled 2 legged oauth in JIRA? See this article: https://confluence.atlassian.com/display/SERVICEDESK/Providing+self-help+resources+for+your+customers+with+a+knowledge+base#Providingself-helpresourcesforyourcustomerswithaknowledgebase-Troubleshootingissueswith2-LeggedOAuth
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!
Unfortunately there are no AUG chapters near you at the moment.Start an AUG
You're one step closer to meeting fellow Atlassian users at your local meet up. Learn more about AUGs