If you see the error message "This item is already being downloaded and added into Chrome" when trying to install AdBlock, this is a known issue with Chrome. It can affect any extension, not just AdBlock.
First try restarting Chrome. If that doesn't help, restart your computer. And if that doesn't help, try this workaround:
- Type chrome://flags in the address bar. Find the text Enable Enhanced Bookmarks and select Enabled in the list below.
- Click Relaunch Now.
- You should now be able to install AdBlock from the Chrome Web Store.
- After AdBlock is installed, put things back the way they were. In chrome://flags, select Default under Enable Enhanced Bookmarks and click Relaunch Now.
If you don't see that option in chrome://flags, turn off Chrome syncing, then try to install AdBlock again.
If that doesn't help, try these basic Chrome troubleshooting steps (perform each step in order, restarting Chrome after each. Only move to the next step if the problem is still happening):
- Restart your computer
- If necessary, update Chrome to the latest version
- Try clearing your cache, cookies, and browsing data
- Try using Chrome in incognito mode, which disables extensions (If that fixes the problem, one of your extensions is the troublemaker - disable them all, then re-enable them one at a time to find the culprit)
- Check for and uninstall any unfamiliar extensions
- Reset Chrome's settings (Programs you install can change your Chrome settings without your knowledge - resetting them will undo any unwanted changes without interfering with your saved bookmarks and passwords)
- Check for and remove malware
- As a last resort, uninstall Chrome. Be sure to select Also delete your browsing data. Then reinstall Chrome.
*Warning: Uninstalling Chrome this way will completely erase your bookmarks, saved passwords, extensions, and Chrome settings on your computer. Before you proceed, be sure to and synchronize everything through your Google account.
If all else fails, install AdBlock manually. How to install AdBlock in Chrome when you can't do it the normal way.