The theme you are having issues with was released before the Vertex framework was developed; unfortunately, pre-framework releases can no longer be updated due to significant changes in how WordPress works. If you are certain that you want to update your site, I would suggest looking at more recent releases to see if there's something newer that you can be happy updating to. The first Vertex release was Paradigm Shift, and the first responsive release was Business Response. I personally recommend not using anything older than Business Response, but that is mainly because the pre-responsive releases that use Vertex will need to be patched with the Vertex Upgrade Patch
before they are fully compatible with the latest version of WordPress.