As nc50lc mentioned, XMR is in high demand and our reserves are regularly empty.

However, as you can see in our last 24h volumes, we have not removed it (nor planning to do for now), and if you would like to get XMR when it's empty you can still open a backorder (this is done like any other order), and awaits for the required reserve to become available. Once the reserve is available, the order gets executed in a priority automatically. Meanwhile the order is awaiting for reserves, there is an option to request for an automatic refund anytime if you consider a refund necessary.