Hi Sairaj,

Although your post lacks of some more detailed information (also the mentioned screenshot is missing), it may be possible that you experienced a temporary internet connection issue or maybe there was a little problem on Red Hat's server infrastructure. Just wait some time and then execute the following commands in a terminal to clean up everything and successfully attach the subscription :

sudo subscription-manager remove --all
sudo subscription-manager unregister
sudo subscription-manager clean

sudo subscription-manager register
sudo subscription-manager refresh
sudo subscription-manager attach --auto

Cheers :)
Christian