@bkushner ,probably because it didnt need to be calibrated ,there is no need to keep calibrating the RC compass ,only do it if asked to in the App ,mine asked for it to be done after the recent RC firmware update that was a fix for those who had problems with the the relationship between the Drones direction and the RC position in the attitude display ,prior to that update it had not asked for a calibration
I've been reporting the same issue since the RC Pro was released! One of the prior FW updates allowed it to actually go through the process, but it has since reverted back to not working again! Frustrating, since the compass is clearly consistently off by some 30°!