While VPN client apps are convinient, they are not necessary. It is possible to configure your iPad for VPN manaully. Below is copyied from the iPad Users Guide iOS 5.1. You should be able to still find and download it in the Books app (assuming that still works for iOS 5.1.
Or here is the PDF version of it i found in a search:
https://cdsassets.apple.com/live/6GJYWVAV/user/ma1632_ipad_ios5_user_guide.pdf
i dong know if this will help, but it's all I can think of at the moment.
“
Network
Use Network settings to configure a VPN (virtual private network) connection and access Wi-Fi settings.
Add a new VPN configuration
Go to Settings > General > Network > VPN > Add VPN Configuration.”
“Ask your network administrator which settings to use. In most cases, if you’ve set up VPN on your computer, you can use the same VPN settings for iPad. See VPN.”
Excerpt From
iPad User Guide for iOS 5.1
Apple Inc.
This material may be protected by copyright.