Unable to update or redownload AOE4 on Steam

Ever since the latest update was offered, I am unable to install the update, or redownload the game (after uninstalling first). The error that keeps popping up is “missing file privileges”.

I am using the Steam version, and I can launch AOE2:DE just fine, as well as other games. I tried clearing the download cache to no avail. The error is the same, before and after the latest NVIDIA driver.