I've got the same issue for my solution, which passes all tests. So in order to finish this Kata I've just used code from chat gpt and it worked

it returns only uniqie elements.
So if you have numbers 1,2,3,5,4,1,2,3 your solution would be 5,4,1,2,3.
Method Reverse makes this array look like 3,2,1,4,5,3,2,1. Then method Distinct removes duplicates (second and all further duplicates), so we have it like 3,2,1,4,5. And next reverse returns an answer 5,4,1,2,3