If upon authenticating your integration you receive an error stating, "Remote error for 'installed': Authentication failed: 401" it means that your Jira instance is rejecting the credentials provided in Aha!
This is not an Aha! error, it is an error coming directly from Jira when we attempt to pass your credentials for an authentication check.
The first step in troubleshooting is to simply ensure you correctly entered your username and password.
SSO and Jira
The most common source of 401 authentication issues comes from customers attempting to authenticate a Jira integration using SSO credentials. SSO credentials cannot be used for API authentication. There are two options.
1) For instances of Jira cloud, customers have the option to generate an API token to use for authentication. This is done through visiting https://id.atlassian.com and clicking API tokens on the left hand navigation. The token can be used as your password for authentication. More details are available here: https://confluence.atlassian.com/cloud/api-tokens-938839638.html
2) Configure a Jira username and password through your profile page within Jira. You may need to set the password associated with your Jira username on the Profile page, too.
If your Jira instance is integrated with Active Directory, you may not see a link on your profile page to set your Jira password. If there is no set password link, you can follow these instructions to set your password: https://confluence.atlassian.com/pages/viewpage.action?pageId=231932759
Authentication errors on a previously working integration
If your integration was previously working, and began generating 401 authentication errors, it means that your credentials in Jira most likely changed.
This typically occurs when your system is set to automatically expire passwords on a scheduled basis.
Authentication errors with valid credentials
A forced update to Atlassian accounts as of May 2017 has also caused some Aha! users to see 401 errors. You can read more about that change and potential workarounds here.