IONOS Python Senior Developer interview questions

They seem like a really good Company. HR was super helpful when rescheduling the first interview because of external factors. After the phone screening, I was asked to work on a Coding Task that took me a couple of days, I did all the parts that were required as well as all the plus requirements, I got feedback days later telling me they liked my solution but something needed to be fixed/improved (they stated that I can leave the task unfinished as the main goal is to see my coding skills). I spent couple days more on fixing my solution, tested in different environments and everything ran smoothly. A day later I got a response saying they'll not continue with my application. When I asked for feedback the only comment that I got it was "It didn't work". I never had a direct interview with the tech team so is hard to know what it really was.