Issues with Fibre Optic - New Build

That's a tough one, nora_okgn. This looks to be specific to your home and without communicating with the techs, it'll all be conjecture.  The specific details may be known to the field and backend teams, though (customer/tech support will generally have a summary of the work performed but not necessarily root cause). Do you still have contact with your installer? Perhaps they are able to offer insight.