Magento Admin login kicks me out back to the Admin login

Question

After I enter my username and password and click \"Login\" it sends me back to the Login page with NO error messages. The URL changes to include a session key and that\'s it

Answer 1

There can be several things that cause this behavior. This is my checklist. One of them will eventually fix it.

1. Click the "forgot password link" and then the "back" link. This will remove any possibly misplaced params in the URL as well as make sure you're on the right server (some installations have separate admin servers)
2. Clear cookies or use an incognito window
3. Try another browser
4. Local installations: Try using 127.0.0.1 instead of localhost (and update the base URL in the core_config_data table)
5. Clear Magento cache, full_page_cache, and session directories in the magento/var/ directory (and repeat 1 and 2)
6. Truncate the core_session table
7. Verify your Magento has correct memory settings
8. Check Magento system.log and exception.log files and debug
9. Check PHP's error logs and debug