I have some additional information. I received this limitation when I first installed the software. When I got home and booted up, I was prompted for my userid and password again and was able to enter more than 20 characters. So it appears to be a problem with the installation process.
I think I have narrowed this one down. It appears that there is a 22 character password limit when prompted for credentials in the small task tray notification window in GlobalProtect v4.1. If you go into Settings -> Sign Out, a different username/password form will appear and I could then input my 24 character password.
Click Accept as Solution to acknowledge that the answer to your question has been provided.
The button appears next to the replies on topics you’ve started. The member who gave the solution and all future visitors to this topic will appreciate it!
These simple actions take just seconds of your time, but go a long way in showing appreciation for community members and the LIVEcommunity as a whole!
The LIVEcommunity thanks you for your participation!