IDM does not catch downloads from a particular site automatically anymore. It works with other sites. What could have caused this?
Maybe you added this site in the exceptions list. When you cancel two downloads from the same site in a row, IDM offers you to add this site in the exceptions list. If you accept the offer, IDM never starts automatic downloads from this site anymore.
To solve such problem, please do the following:
1. Open "Option→File Types" dialog and press "Edit list...":
2. Then find you site in the list, select it and press "Delete".