@Lindsey260 I personally find it a little sleazy for guests to ask for discounts and refunds - it's often a sign of trouble ahead. However, when a guest reports that a listed amenity isn't working, I'd recommend that you reach your final agreement on how to resolve the issue before taking action on it. If you don't believe that the situation warrants a partial refund, the guest should have the option of terminating the rest of the booking and accepting a refund for the unused nights - basically the professional way of saying "put up or shut up."
If I were in your situation here, though, what I would do is initiate a Resolution request with the amount of compensation I was willing to offer (50% off one night's room rate is my default remedy when it's a one-night problem). Don't ask the guest to initiate the request - it looks more professional if you present your offer than if you ask the guest to state their demands.