I'm playing for the "For Odin" achievement, and I hold all of Denmark and Norway as a Norse country. A Protestant Center of Reformation (CoR) was formed in Akershus, adjacent or very near 10 of my provinces. None was ever converted, even after all of Sweden was converted. Likewise, Scotland has a Reformed CoR and it has never converted Faroarna. I'm 70% into converting Akershus (about 15 years), and it has never tried to convert my provinces. I've also noticed that Orthodox Novgorod hasn't any converted provinces either, although it might be out of range of the CoR. So does anybody know if a CoR can change none-Christain countries (or Orthodox)? Thanks.
Centers of Reformation can only convert provinces from the Catholic religion since that's the religion the Protestants split off from. For Orthodox or Pagan people it wouldn't make much sense to be 'reformed', because they're a different religion in the first place and don't have the issues that the Protestants would criticize (Papal power, indulgences).