Are you experiencing issues writing to NTFS Formatted drives after upgrading to OS X El Capitan? Then you might have to reinstall Paragon NTFS for Mac OS X.
Before you reinstall, you can try disabling and re-enabling usage inside of the NTFS for Mac OS X panel inside of System Preferences.
To reinstall, simply download the current version from Paragon's Website here.
I am currently using v 14.0.332