I don't think a mere number will make that much difference. tp has more associated people than several natural languages (though they may not have ISO code either) and a reasonable amount of press and a small but quality library. But it has no organization at all, just websites that call themselves tp something but are not connected, except possibly personally. So, there is no organization pushing for recognition. Nor are we owned, in some sense, by a big company, which might think an ISO worth having for their spawn (I don't know if any of these languages Na'vi, Klingon, Dothraki, etc. have ISO, either). In addition, the organization that gives out these labels is not very forthcoming (nor clear when it comes forth) with guidelines for what is actually needed to get a label. At a guess, behind all the facade, it is just some bureaucrat saying Yea or Nay, more or less on whim.