Visa rejected after interview

As an international student, I got a visa interview and was rejected on grounds of not being a genuine student according to the caseworker. I have emailed the university enquiring about what action should I take next and haven't recieved any reply yet. With the registration for my course starting on 15th september I fear it's too late to reapply for a visa. I can apply for a priority visa but with the slow process I am not sure if I'll get positive results by the deadlines. So i want to defer my studies to the January intake. Is there a precedent for this? And how likely am I to recieve another CAS from the university? Whether to reapply right now or for the January session? As i genuinely like the course and the university and am serious about pursuing it. Please any advice would be helpful, thank you 🙏🏻