If you are using Firefox, open Firefox, and inside Options, go to the Applications tab.Next time you click the Download with Manager button, Chrome should pop-up a dialog asking to launch the application registered for nxm links.Delete the line that says "nxm": false (if true, still delete the line).Search for "nxm" (Click Ctrl+F and enter nxm).Open the file in a text editor such as Notepad while Google Chrome is closed.Locate the "Local State" file (enter %LocalAppData%\Google\Chrome\User Data\ in the Windows Explorer address bar).If the program is not pointing to Mod Organizer, right-click in the window and select Add, select the game you are handling, browse to the appropriate ModOrganizer.exe application, click OK, click the Register Active button, click yes at the prompt, and close. If the program is pointing to Mod Organizer, click the Register Active button, click yes at the prompt, and close.
Problem: When I click the Download with Manager button on the Nexus, nothing happens. Proper debugging of downloading with manager issues should follow the troubleshooting instructions on the wiki: You do not need NMM for MO to download mods.