Did you already do the free trial? If not, message support.
I had this happen to me. Support told me to contact Apple. Apple support told me to contact the app customer support. Neither could tell me why it was not working. I then remembered that the last purchase I made was with my iPad, which I quit using to play. I got on my iPad and tried the purchase again and it worked. So if you have recently switched devices, that may be the problem. Hope this helps.