Okay, so you've done the easy, quick, once over. Now it's time to get serious (and your wallet out). That means you get the "Deere people" (or maybe if you're lucky, someone else that knows the system and has the necessary tech savvy and equipment to trouble shoot it) involved to figure out WHY the computer doesn't like what it sees. Possibilities are many, and no one out here can tell you which one is most likely. Computer controlled transmissions are great when they work, but not so much when they don't. Self experimenting isn't cheap either. The various pressure switches, sensors, solenoid coils, ETC can be crazy expensive.