Transmission Problem?

I have a automatic A4 1999 Quattro with 165,000km. From parking spot would not go in reverse till someone gave it a push. There was a clunk
and then it moved. Engine light "check engine" came on, it reversed - went forward and back and forward and back and then I returned it to its parking spot, where it still sits.
Any ideas as to what the problem is now?
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