There might be a problem with the sim, your phone might not be able to read it... most phones require a sim card built specially for them. I'm not sure that that would be the problem though, when I dont have service I turn on airplane mode for 10 (or more) and my signal usually returns. Hope this helps!!
What kind of fuel does it use? I have similar problems but with a weed eater, if the fuel is the kind that you have to mix yourself you may have used the wrong ratio. In this case check the spark plugs to see if it is running rich or not, then remix the fuel according to manual. I have limited experience with tractors but I really hope this helps you!!