USB install - ISO not available after repartion

I created a USB thumb drive with RHEL 7.4, boots fine. When i got through the setup I can see that I can select the thumb drive and the iso on the thumb drive for the source. When i configure the destination and repartition the target drive, click done and go back to the source it does not list the thumb drive. It disappears. No trouble installing CentOS or Kali on the same box. VR, km