This is most often caused by a problem with your internet connection. Please check your internet connection and retry. marketplace.eclipse.org
- Go to-Window->Preferences->General->Network Connections
- Choose "Active Provider" To "Direct"
- then click "apply" and then "ok".
- Open command prompt (windows start button, type cmd in search)
- Click top left of command prompt, click properties, enable quick edit mode
- Copy: setx _JAVA_OPTIONS -Djava.net.preferIPv4Stack=true
- Right click on command prompt, should paste
- Hit enter. That easy!
I tried all the suggestions but no success for Eclipse Mars, Neo and Oxygen At last it worked for Eclipse Oxygen when I added following line to eclipse.ini file