I was targetting to get the PSN Plus offer (buy one year membership get 3 extra for free) on March 4th, but due to the maintenance happening during that time, I wasn't able to purchase the subscription till March 5th. Can you help me with getting that offer? My order ID is 3769443171
This forum is not a method to contact Playstation customer support. That has to be done by phone or live chat. Although the announcement of the promotion says that it ends on March fourth, the promotion actually ends when the Playstation Store is updated later today, whenever that happens. It hasn't happened yet, so you should have received the three extra months already.