Security software often identifies DLL files as potential threats and moves them to quarantine.
Replacing system-level files with unverified versions can lead to Windows crashes. Optimal System Requirements for RE4 UHD download steamapidll resident evil 4 uhd full
The Windows registry might have an outdated path for the file. How to Fix Missing SteamAPI.dll for RE4 UHD Security software often identifies DLL files as potential
If you have tried verifying your files and the error persists, it might be helpful to know: Are you using any (like the HD Project)? Which operating system are you running? Did this error occur after a recent update ? your antivirus might have "captured" it.
If the file disappeared suddenly, your antivirus might have "captured" it.