I had a problem with the app last night, but not the issue you're experiencing.
Voting eventually worked ok on my old android smartphone (once the show had finished and it was presumably less busy), but I couldn't even get the app to load on my up-to-date android tablet, despite re-downloading it.
In my case, it's nothing to do with restricting in-app purchases, as I do that on all my devices and it works ok on one, but not the other. I only tried the app on 2 devices, so nowhere near their 6 devices limit.