Dear Apple Valley:
I'm not sure if you have filed a lawsuit or not -- you don't have to file one to go to mediation.
You may have been in mediation because of the pre-litigation requirements of Civil Code §895, which requires parties to try to work out problems with homes before a lawsuit is filed. That should have been what happened, if the builder agreed to make repairs.
A builder/pre-fabricated home manufacturer cannot actually appeal a decision reached in mediation, so either you weren't in mediation (it could have been arbitration), or the home manufacturer breached the agreement you reached in mediation.
If the builder breached a mediation agreement, your attorney needs to move to have it enforced. How that would happen depends on what was going on with your case, procedurally.
By the way, governments have extremely broad immunity for inspections. That means even if they should have realized there was a problem with your home, you cannot sue them.
The Statute of Limitation for filing an action based on patent (obvious) construction problems is four years from the date of completion or certificate of occupancy, whichever is earlier. Make sure you take action before that time runs out.
There is one thing that you might try, although it is a little unorthodox. If you can figure out who the builder/manufacturer's insurance company is (your attorney may know), you could try writing to them and seeing if they can intervene. They do not have to do anything until their insured is sued, but sometimes they will to avoid a lawsuit.