: Right-click the game in your library > Properties > Installed Files > Verify integrity of game files .
Security software is essential for protecting your PC, but it can sometimes be overly aggressive and mistakenly quarantine legitimate game files. It's possible your antivirus software has flagged the bigfile.000 file as a false positive (an incorrect threat detection), moved it to a quarantine zone, or is blocking the game from accessing it. This issue has been reported as a common cause for this error. Rise Of The Tomb Raider Unable To Open Bigfile.000