It could be a problem with the position of the code on the page. It is difficult to say without looking at it, but the random password is generated with two essential chunks of code... an include file that contains the function that actually generates the password, and a line of code on the page that calls that function and usually stores it as a session variable to be used later.
If it isn't working, one of those two things is out of place or referenced improperly. If you continue to have problems, post a support incident... this will give you an opportunity to share your files and webassist can debug them directly to determine the precise problem.