It does occasionally happen that files will become corrupted, but fortunately Steam has a way to fix that. This fix is for the Steam version of the game. At the very least, it can't hurt to give it a try. But turning it off and back on again might just resolve the whole problem.
This is a pretty simple fix, and is generally the first one for just about any tech issue. How to Fix Unable to Complete Version Check in FFXIV Fix 1: Restart Your Router or PC But even so, here are some of the best fixes and workarounds that we've found for the error. This particular bug seems to pop up more often right after a patch. Though this problem isn't new, there aren't a lot of surefire fixes.
Final Fantasy XIVis not immune to these problems - and for years people have been receiving an error message stating 'Unable to Complete Version Check'. Unfortunately, this constant need to update the game leaves room for mistakes to be made and problems to arise.
