White wood slat venetian blind (New Ash Green DA3)

White slat blind, I think it's around 180cm wide. Please note - I bought this second hand, but before putting it up I tested it, and it was jammed and wasn't releasing down. As I tried to pull it the cord snapped. I think it can esisly by unjammed, as I since fitted another one that was like that, and released it just by using a screwdriver to release the mechanism. But not sure what to do about the snapped cord