Why does only one wiper work on my 2007 dodge ram?

Dodge uses a plastic wiper bushing (ball and socket type) that connects the motor and linkages. It is designed to break before other more expensive parts, it can wear/dry out overtime. You can check by removing the wiper arms then cowl cover. You can check if it wore/popped off, it is loose, the part can be picked up from an auto parts store. I replaced one on an older dakota, the pack came with 2 was <$10. It is pressed into the linkage, can be difficult, but I was able to do it with channel lock pliers.