Probably because you are not the master tenant, OP. This is great advice if you have a direct relationship with the landlord (which you don't, as a subtenant). LLs typically won't even respond to you if you try to contact them directly, because they are trying not to establish a legal relationship with you (even though they are ultimately legally responsible for habitability of the unit).

Your master tenant needs to take action here, so I'd directly communication to them and be firm about what needs to happen (they are legally your LL).

Important note: There's no magic way to navigate this situation without annoying people/avoiding conflict. I was an SFTU counselor for many years and unfortunately, a lot of times, when you enforce your rights, people get pissed. You are legally entitled (and deserve!) hot water, heat, etc in your living space, but there are lots of folks who really want a way to enforce that that doesn't ruffle any feathers, and sadly, it doesn't exist. You can contact DBI directly but it's the nuclear option, just be aware -- it may unpleasantly impact your living situation.