When I installed the template, the shaper_helixultimate template was not installed as part of the package, even though PageBuilder is installed.
The problem was when I went into Templates: Styles (Site) > investa - Default > TEmplate Options the control menu on the left of the screen was not presenting properly.
When I installed the shaper_helixultimate template and worked through it to set up the site, the menu was fine and the 403 error disappeared.
There is something wrong with the template or maybe it is the process of installing the template and not including the shaper_helixultimate template that is at fault.
See the screen shot of the template at https://www.accountantswebdesign.us/screenshot.jpg