I'm sorry but maybe your algorithm is not efficient enough. There are amongst others four tests with 9 digits numbers. It's cheating but in Ruby you can try to use the 'Prime' class (I don't use it and my solution takes 500 ms), you'll be less disappointed...

Another problem is that we all get a given time for every language, with no chance to set it up, so in some languages a kata may be tougher; if you tried my JS version, I warn you that solving it in the given time is surely harder than using Python or Ruby (I tried using the same exact code, but it took too much, so I pulled out a trick or two out of my neophyte hat).

Is your language Clojure? There are some relatively big numbers but not a lot of tests so I don't think that your solution is too slow. Unfortunately Codewars has, too often IMHO, problems and times out or gives weird errors when it is too busy... Try later and tell me if you eventually succeeed or not.