Hi...
You can't use the CC3 version of the Iray Plug-in with CC4 but you should have the CC4 version as well in the Reallusion Hub. So please check in the Hub to see if the CC4 Iray Plug-in is listed in the Add-Ons section for CC4. If it isn't, please then check in your
Reallusion Account to see if there is a banner displayed with a link to upgrade all your plug-ins.
However, if you still have problems after checking, please contact Support using the link below. They will be able to help you with this.
https://www.reallusion.com/CustomerSupport/UserEx/QForm.html
Peter
Forum Administrator
www.reallusion.com