It only needs to be one sensor failed to shut the whole system down on the factory fit ones. I had exactly the same problem with mine and a quick tech2 session discovered which one was faulty (rear passenger side in my case), I replaced that one sensor and it all works fine again.
You need to get someone to check the system with Tech 2 for you, either pay a dealer to do it or see if anyone on here is in your area that has one. That will tell you the problem sensor(s) and then get yourself on Ebay and pick up a replacement (they're a LOT cheaper on Ebay than at the dealers).
HTH
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