No problem, The sample tests in C# seem fine, and there is a fixed test for n = 10 in the final tests:

Assert.AreEqual("Great, now move on to tricks", Kata.HoopCount(10), "Should work for 10");

That also looks good.

And that's what you're asked to do:

If Alex gets 10 or more hoops, return the string "Great, now move on to tricks".

Your code returnrs true for a = 100, b = 1 and c = 1.

Did you read all the way to the end of the kata description? See this part:

Input validation

If an empty value ( null, None, Nothing etc. ) is given instead of an array, or the given array is an empty list or a list with only 1 element, return 0.

I just looked and I see that this kata has been solved 2416 times in C# - do you have a specific problem, with specific inputs/results that makes you think you have found a real error with the kata? Because 2416 other people seemed to solve it OK.