The most common reason a Public Mobile SIM doesn't work in an iPad is that the APN (Access Point Name) settings aren't automatically configured for data. Since Public Mobile is primarily a phone service, iPads often don't "know" how to connect to their data network without manual help.
If your iPad shows signal bars but "Could not activate cellular data network," follow these steps.
Go to Settings > Cellular Data > Cellular Data Network.
In the APN field under the Cellular Data section, type: sp.mb.com (leave Username and Password blank).
If there is an LTE Setup section, enter sp.mb.com there as well.
Restart your iPad once finished.
The SIM must be activated on a plan with data through the Public Mobile App. It is often easiest to activate it in a phone first to ensure it's working.
Carrier Lock: Ensure your iPad isn't locked to a different carrier. Check this in Settings > General > About under "Carrier Lock" (it should say "No SIM restrictions").
Public Mobile SIMs are slightly thinner than some others. If you see "No SIM," try placing a small piece of scotch tape on the back of the SIM (non-chip side) to help it press firmly against the pins.
Try resetting Network Settings. If the APN settings are correct but data still won't connect, go to Settings > General > Transfer or Reset iPad. Tap Reset > Reset Network Settings. Note: This will also clear your saved Wi-Fi passwords.
If there are still issues, you may wish to post for assistance on the Apple iPad forums.
