After reordering User Directories in JIRA an administrator can't login any longer despite providing correct credentials.
There is a duplicating user with the same username in the directory in higher position. Currently, JIRA does not support 'shadowed' users. This is a known limitation tracked in JRA-23861 - An admin can lock themselves out of JIRA by changing the order of the User Directories.
Ask for assistance another administrator and ask them to revert the ordering modification.
Temporally disable the directory in the higher position with help of SQL. Ensure that you have valid backup of your data that could be used for the restore, if something goes wrong.
List all currently defined directories:
Disable the conflicting directory. In our example we will disable directory with ID 10102: