Hi There,
Sorry for the inconvenience.
Please let us know your phpBB version. If your phpBB version is less than 3.1.10 or 3.2.0, then update your phpBB version. This is because, our ForumUS phpBB style only support phpBB version 3.1.10 & 3.2.0 that we have provided separately in the main_files.
Moreover, please follow the installation instruction carefully & properly from the documentation, that we have provided with the main_files.
Best Regards,
ThemeLooks Support Team