Welcome to the forum
Can you give more details? What did you do exactly? Are you using a private tracker? For what I know in private trackers it is mandatory to have at least a 1:1 ratio, so if your ratio is under 1:1 the administrators prevent the user to download further until the ratio is not good (or in worst cases they can ban the user).
The only solution is to upload as much as possible until the ratio is good enough to enable again the download feature