IOS 9.3.5
iPad Air
Connect your device to your computer and restore using iTunes.
I tried but iTunes does not recognize the Ipad... it's like it's not connected.
iTunes recognize the iPad and it says that it is reinstalling. But then appears "error" and it starts reinstalling it again.
What is the exact wording of the error message?
it's in portuguese and says it was impossible to restore and then something like error 21.
That may be a hardware issue. See this article:
IOS 9.3.5