do you get thousands of results showing available but none download? if that's the case make sure you have the latest patch installed (
www.winmxgroup.com, should say Patch Operational at the top of winmx once installed) as it could be fakes
or are they ones not showing as available? in those case select "Auto Enter Queue" on the search results before download and change it to 100 to join their queues which are probably longer than you are set to
if you click the + next to the download as soon as it goes red (it disappears after a bit on default settings so do it straight away) then it should list the exact reason for the error which would make it easier to say what the problem is