Tipalti Software Development Team Leader interview questions

I've been approached by mail, then by phone by talent acquisition in Tipalti. She briefly described what Tipalti do, I described myself, then she asked me if I'll be ready to do some 2 hours long home assignment. She explained that if I'll exceed the supposed time, that will be OK, but will slash a bit the final interview result. After seeing my solution, they just sent me a mail with the following resolution: "I am sorry to inform you that your home assignment does not meet our requirements.I want to thank you once again for your efforts and wish you all the best." I sent a mail asking the explanations regarding what was wrong in my solution? But nobody returned a mail or call with an answer.