@Lizzy32
I believe that with your booking request you will have already made a payment and you are awaiting host approval. It is true that the host has 24 hours to either approve or cancel your request, and they need to provide some reason for that or incur penalties. They wouldn't want that.
You, on the other hand have 48 hours to cancel without any loss. If you cancel within 48 hours you will get a refund. What I would do is find an alternative accommodation, ENQUIRE with them if it would be OK to book for your chosen dates but you need to confirm some further details like; that you are are attending a university conference and you would like to know the easiest way to get to the conference from the accommodation and how long it might take... Then nearer the end of your 48 hour period after awaiting any response from your first host, cancel your first host and book with your next choice subject to an acceptable answer.
You might also check with Airbnb why you have had no confirmation or cancellation of your booking request.