Invalid MAC

This error is usually caused by resetting your app key, which is used for security. It can be fixed by clearing the sftp_password column in the database. This can be done as follows:

First of all, you need to login to MySQL. This can be done with the following command:

mysql -p

Next, select your panel database. I'm using the default panel database name here:

USE panel;

And lastly, we need to actually update the database columns. The command below takes every entry in servers and sets sftp_password to NULL, so it isn't set anymore. This won't change existing passwords, and only prevents them from displaying on the panel's side.

UPDATE `servers` SET `sftp_password` = NULL;

If you haven't already, exit the MySQL client with the following:

EXIT;

You should be good to go, however you will need to re-enter your SFTP password in the "SFTP Configuration" tab.