Reason. IDM is not allowed to download or run in Firewall settings. Many FireWalls check the size of application executable file that try to access the Internet. That's because a virus can replace the file with its own, and get access to the Internet. Probably when you updated IDM, its executable file size changed, and your FireWall blocked the Internet access for IDM. If you have a FireWall installed, please check that IDM has appropriate access rights.
Solution. Change incorrect Firewall settings. Please choose instructions for your Internet Security (Firewall) software below: