It is impossible to enter more than 14 characters in a password. Why?
Article ID: 743, created on Oct 6, 2008, last review on May 8, 2014
Plesk for Linux/Unix
The length of passwords is based on the length restriction of passwords for every particular operating system. By default it is 14 symbols maximum. This is why there is a restriction to 14 characters maximum in Plesk as a general policy.