Check if captchas are activated. It might help to login via browser once. If the login was possible before, you can also check if you need an API Token. To handle this, proceed as follows:
2. Login with the user that should be used as sync user.
3. Create a API-Token (Save your token somewhere save. The token is able to bypass Multi-Factor-Authentication via API)
4. In Jira Sync use the email-address of the user that created the token as username and the token as password.
5. Use Jira Sync like before.
Failed message
Server not reachable, check connections
Nothing is synced
a) Check if you productively use the Jira sinc user in aqua. If so the sync will not work
b) Check the timezones of your Jira and aqua environment.
Sequence contains no elements
Wrong IssueType.
No jira user found
Check with jira addon 'REST API Browser', if the user can be found via email or username. Add '/plugins/servlet/restbrowser' behind your jira URL to open the addon after installation and search for the users using the user picker (api/2/user/picker). Check if your jira user has the permission to search users.
