Why do my downloads stop as soon as they start?

First, check the exact error shown in your browser's download list. That can tell you whether the problem is the network, the file being blocked, or the destination folder.

Also check that the drive has free space and that you can save a small file to the download folder. If not, try another folder to see whether the original location is read-only or otherwise inaccessible.

Since it's happening across different sites, take a look at your VPN and proxy settings. In Windows 11, check Settings, Network & internet, Proxy for anything unexpected. If a VPN is connected, try disconnecting it temporarily and testing a download.

Firewall and antivirus scanning are separate things. Check your antivirus protection history for a blocked download or an error around the time you tried. That may give you a reason without turning protection off.

Try restarting the router, then test a small download again. If it still stops right away, the specific error message will be more useful than guessing at the cause.