ALWAYS download and install the official patch always. You always want to do this. Did I mention always?
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If you do not have the Throne of Bhall expansion game installed for some reason, then you need to download and install the Shadow of Amn main game patch. Do NOT use the ToB expansion game patch.
If you have the ToB expansion game installed, then you do not need the SoA main game patch, because the expansion game patches the main game. Instead, you should ONLY download and install the ToB expansion game patch.