Please note that if you import the YubiKeys information, it will be stored in the locally installed OTP validation server. So if you want to use the locally installed OTP validation server, then from "Global Configuration" select "Local validation server on RoP and make sure that you are able to authenticate the OTPs with the locally installed validation server and then try to assign the YubiKey to the user.
Regarding testing, you can use the Radtest utility, which is already installed on the RoP VMware image. For more information, please refer to the section "4.2.7 Testing the configuration:" of the "Yubico_Radius_on_Premise_VMware_image_configuration_guide_V2.pdf" guide available at
http://wiki.yubico.com/wiki/index.php/R ... Premise-IIWe hope this helps!