I was referred and a recruiter reached out about a week later. I scheduled a call with the hiring manager and asked in advance what this call would consist of. I was told that it would just be a resume review.

When I got on the call, I was asked how well I knew some of the optional requirements and then asked to solve a LeetCode Hard problem with only about 15 minutes left. However, it was one I had seen before, so I was able to provide the correct answer. After that, I spoke with the hiring manager for well over the time limit about the job and their personal experiences working for Microsoft.

I was almost certain I was going to be moving forward, as I really enjoyed the chat I had with the hiring manager and was able to solve the question even though I was asked it by surprise.

The only thing I can think of is that I didn't know some of the optional requirements that well. In that case, they should have been required instead of optional to avoid wasting anyone's time.

I was also ghosted until I followed up multiple times.

NDA, but it was a LeetCode hard on the Microsoft list.