[XB-49]

Sound Mod was the mod you had to install to allow your game to accept mods before the Unified Installer. There is a wrapper in the Unified Installer but is different to the wrapper for each new plane. I'm not sure whether the latest AC Installer 3.8 buttons file is included in UI. But just to be safe, I suggest downloading it. Here's a link to the AC Installer 3.8 (The link is inoperative) Download 3.8 first, then download your aircraft. Don't download the old version of AC but install the wrapper.

Hope you get your new plane soon!