There may be several reasons why the VPN software if not connecting, try the following below as it may resolve the issue.
Issue:
Mac OS user's Global Protect VPN software is displaying Connecting... Still working message and won't connect to the VPN
Possible Solution 1:
1) Navigate to System Preferences.
2) Locate and click on the Security & Privacy icon
3) Click on General and at the bottom if there is a System software to allow please click on the Allow box as stated on image below.
Note: If you cannot click on Allow than you may have to unlock System Preferences first.
To do this; click on the yellow pad lock at the bottom corner (the one that says Click the lock to make changes) and authenticate with your computer username and password. After that click Allow again.
4) Return to the Global Protect VPN software and see it the connection is successful.
Note: You may need to referesh the connection. To do this; click on the 3 lines on the top corner of the VPN software and select refresh. If that that does not work you may need to restart your computer.