Acne - Duac doesnt work anymore. Duac?

Hello Doctor, This is arun here, so for past 1 year i have been using duac once daily medication prescribed by my local doctor for my moderate acne condition and it working so good but then after 1 year it seems like it doesnt work anymore and i was still continuously taking the cream weekly once and every other day, whats the issue here, and yes i also do exfolaite my skin using the cosrx power liquid but i use it every other day, i dont use both duac and exfoliator at the same time, i use a mild face wash from aroma magic neem and tea tree face wash, so am really confused what am i doing wrong, i did some research and its told that duac supposed to be kept in the fridge or it wont work, but for almost 1 year from the day i bought am storing duac in the fridge, So what went wront with duac? Should i continue using duac or switch to benzac 2.5 which only has benzoyl peroxide. Thank you in advance