Why isn't the Download Accelerator Plus triggered by the Browser?
If you are using any other download manger that also integrates into the browser, it might interfere with integration of the Download Accelerator Plus.
To re-enable the triggering/integration of Download Accelerator Plus, open DAP, click the "Tools" menu -> "Options", enter "Connection" on the screen that you get and set your browser integration and then restart the browser. Also check, on the same screen, to see if DAP is checked as your Default Download Manager.
If for some reason you disabled dap (by choosing either the "Disable downloads by DAP" or the "Exit and Disable downloads by DAP" from the taskbar menu, you may enable triggering again, simply by right clicking the taskbar DAP icon, and choosing "Enable downloads by DAP (Acceleration On).