Insulation missing

Who is liable? I discovered my town home built in 1999 lacks insulation and any type of vapor/moisture wrap in the bottom level (not enclosed by by neighbors, it is an extension) through getting worms in when it rains and cold air blowing in the electric switches.
The HOA says structural issues are the homeowner responsibility. I know several other tennants have found the same problem.
Who is liable?

Did you have it inspected before you bought it? If not, then the answer is most likely, “YOU”.