The "All slots for slow download are in use" error typically occurs when you're trying to download a file from a server that has a limited number of slots available for slow downloads. When all slots are occupied, the server refuses to accept new download requests, resulting in this error message.
Why? Most free downloads take 30–90 minutes due to throttled speeds. After a download completes, the slot is freed. If you wait 15 minutes, there is a high probability a slot opens. The "All slots for slow download are in