Some iZotope plug-ins are not available to load in Reason. This includes RX 10, Ozone 10 and Neutron 4.
Reason is not currently compatible with VST3 plug-ins. Due to Steinberg dropping VST2 support, Ozone 10, RX 10, Neutron 4, Symphony 3D, and Stratus 3D have been developed with the current VST3 format.
Reason have mentioned on their blog that VST3 support is coming soon.