No errors are seen by the user or shown in event logs on the server. The logon script is delayed by up to 5 minutes which has been observed from Windows 8.1 or Windows 2012 machines users.
If you manually execute the user script from within the users session it works fine. The same issue can be seen in a Microsoft's Remote Desktop (RDP) session.
Using GPEDIT.msc, adjust the Microsoft Policy called Configure Logon Script Delay for your Windows 8.1 or Windows 2012 users.
The policy is located here:See Microsoft TechNet Blog - Windows 8.1 Logon Script Delay Policy Setting.
This issue is caused by a policy introduced in Windows 8.1 by Microsoft to provide users a faster logon to their desktops bypassing delays which users may experience due to lengthy logon scripts.
Microsoft TechNet Blog - Windows 8.1 Logon Script Delay Policy Setting
Microsoft Forums - Logon script delayed by 5 minutes (300 seconds)
Microsoft KB2895815 - Logon scripts do not run for five minutes after a user logs on to a Windows 8.1-based computer