I'm having the same issue and I've also contacted support. Unfortunately, it seems like right now there is no solution and what's worse is that there might not be one in the near future. I saw a post here from someone with the same issue that was dated 4 months ago, so my hopes that the issue will get fixed soon are not high. PVZ 2 Game Unresponsive. | EA Forums - 10265662
Fortunately, there is a way to get around it. The way I've been doing it is going through the missions tab, but it sounds like you can also do it through the plant almanac by: going to the arena -> plant almanac -> any plant -> find more -> world. It sucks, it's inconvenient, but it's a work-around.