Downloading a file from third-party "DLL fixer" websites is generally not recommended . These files are often associated with cracked video games (specifically those using "CODEX" emulators), and downloading them individually can lead to malware infections or version mismatch errors. Why you are likely seeing this error
GOG games, in particular, are DRM-free—no cracks needed. And they often go on sale for just a few dollars. codex64.dll file download
If you use Windows Defender (or any major antivirus): Downloading a file from third-party "DLL fixer" websites
If you see codex64.dll listed, you can "Restore" it—but only if you trust the source of the game. : codex64.dll file download