The code assignment was just 3 ASP.NET API endpoints, they asked for TDD and integration tests. They don't give a lot of details on additional requirements or expected architecture design, so you need to be creative and apply your knowledge to build a nice solution.

I was supposed to have a Technical Conversation, but just before, the Technical Interviewer told me that he will cancel the call and stop the recruitment process because I don't have too much experience on building apps from Scratch.

I have 8+ years of experience as SDE and this is the first time I get rejected because of not having too much experience building apps from Scrach. I feel like I could give more explanation on why I have not worked too much on building new apps, and what other skills I have that might be useful for the role/company, but without a formal call there is no way.