Invisible Technologies Senior Software Engineer interview questions

The interview process had the following stages: 1 Hr call - he talked really fast and told he is to hire 20 people. Then interview with engineering manager — came pretty good, then HR sent me tech assessment. After that I had an onsite interview in Warsaw with 3 top managers & 1 staff engineer. The interviewers asked in details about my projects and vision, the final round was technical design. I came prepared and thought it came fantastic and I did a great job! However, 3 working days after I received generic rejection, which was unpleasant surprise for me. :( I asked HR, what came wrong, but was ghosted.