credentials?

I have used Pocket Cloud for a few years. I have installed the companion software on my laptop, my wife's desktop, and our church office desktop. Recently the church replaced the desktop with a laptop running Win XP, sp3. This is the same OS that ran on the previous desktop.

When I open Pocket cloud on my android, I see the new computer and all my others. However, when I try to connect, I get an error message that says "invalid credentials." I set up the user name and password myself on the new laptop and on the android pocket cloud.

why, if I can see the machine I cannot connect properly? Is there a mandatory size the password must be? our pastor instructed me to use a three letter password, despite my warning that it was not strong enough.