KidsLoop Senior Software Engineer interview questions

A waste of time. I had already spent a weekend completing a complex coding assignment. I got exactly the right answer, turned out impeccable code with lots of good unit tests. The interview was at 8.20 in the morning on webcam. The interviewer was wearing a mask; he seemed unfriendly right from the beginning, straight down to business with no pleasantries. The interview was just banal stuff. Where have you worked, what language do you use etc. The feedback was that I'm smart and good with complex coding tasks but there were concerns that I can't collaborate. Okay, why? I have had no trouble collaborating before. I keep my ego in check; I'm known for being a nice, friendly person. So I certainly wasn't pleased to have to go through that dance only to be told basically that the interviewer doesn't like my face or has some kind of prejudice which leads him to assume I can't "collaborate".