Hi,
Try reinstalling LR 11.5 by logging in as "Administrator".
I had the same problem. unregistered class file {CF405F74-C2F7-4814-AD81-525877D8C9A0}. This happens when your user account on the system does not have complete admin rights and hence the class files will not be regestered in windows registry properly.
Solution: Uninstall LR 11.5
Log in as Administrator.
Install 11.5 again.
Thanks,
Brijesh Mishra.