Offline and Online devices constantly

Hi.

My devices constantly go offline and, in lesss than a minute, it returns online.
The devices, Coban TK103A, are configurated to send the position every 20 second.
I tried to configurated the protocol timeout to 25, 30, even, 300 but the notifications continue to be sent

Give me your advice please

It means that your device disconnects from the server by itself.

And what could I do to solve this?

Check with your device vendor. The issue has nothing to do with server side.