Some software will not load from GUPDATE.GCD but will if done via an *.rgn file with updater.exe in pre-boot mode. If you aren't sure what you are doing (especially cross-flashing or using modded fw) it is quite easy to brick your device using an inappropriate rgn.
It seems unlikely to successfully flash to PH on your US device using GUPDATE.GCD. Probably it did not load the PH fw at all. Did you check it on the unit's inventory or in GarminDevice.xml?