Transfer Tool is unable to fetch an account list from a Plesk server

Question

Why is the Transfer Tool unable to fetch an account list from a Plesk server?

Answer

This is caused by the Plesk server being unable to authenticate to the MySQL CLI (Command Line Interface). You can verify this by running the following command on the Plesk server:

mysql

If there is an ERROR in regards to access being denied, you want to ensure that the correct MySQL credentials are specified within all of the following files:

/root/.my.cnf
/etc/psa/.psa.shadow
/etc/mysql/conf.d/client-mariadb.cnf (if exists)

If the above-provided files have the correct MySQL credentials specified within them but it's still not possible to authenticate to the MySQL CLI, MySQL may also read startup options (if defined to do so) from the following files, in the below order that you will also need to ensure have the correct credentials if they exist:

/etc/my.cnf
/etc/mysql/my.cnf
SYSCONFDIR/my.cnf
$MYSQL_HOME/my.cnf
defaults-extra-file (The file specified with --defaults-extra-file=path, if any)
~/.my.cnf

If the MySQL password is unknown, please refer to the following article for details on how to fix the password (if using Plesk Obsidian, proceed to the Manual solutions at the provided link) :

https://support.plesk.com/hc/en-us/articles/213364309-Unable-to-access-Plesk-on-Linux-after-manually-changing-the-MySQL-admin-password-Access-denied-for-user-admin-localhost-using-password-YES-