Apartment AC isn’t cutting it

So our apartment's air conditioning has been struggling all summer. Typically set it to 77 during the day but it consistently climbs to 81-83 by 3pm. We have bought curtains for all the windows which barely helped.

We have contacted our apartment's maintence at least 5 times but we have seen little to no improvemt. The maintence team is just one guy and he doesn't seem to be knowledgeable enough to fix it. It seems like the main vent in the living room is not getting any flow but the other vents are. I have tried taking the cover off to look for broken ducting but didn't see anything obvious.

So, what should I do? The temperature is annoying but it's our outrageous electric bill that I'm so frustrated about. Any advice is greatly appreciated.