Happened to me as well
I use the prepaid Internet microsim
Here're how I solve it:
1-Go to Settings ; turn off wifi and turn on cellular data to use it
2-Using the iPad Internet browser, navigate to www.aljawal.net.sa
3-click on JAWALNET>SUBSCRIBE>chose the Internet package you paid for and BUY
once you do that, the microsim is activated and you can browse the Internet normally
Good luck 