When there is a significant volume of user requests, the server overloads or becomes congested. This frequently happens when a significant software update is available for download and a large number of people try to upgrade their devices at the same time. When this happens, the server becomes overburdened with download requests and eventually goes down. Your request will most likely be queued and handled once all other requests have been finished and the server load has decreased. . Usually if this is the case, you will see an alert message telling you that the server is currently unavailable and that you should try again later. And so, you have to do as it says.