Plugin problem

Nop-Station OCarousel this plugin after installation it ask for key and after entering the License string key it give error (Your product key is not valid for this domain.) why.

Do you download this plugin after entering your domain url? From here
https://www.nop-station.com/nopstation-ocarousels-plugin

Yes i am do the same way but its not working it give error like this:-

We're sorry, an internal error occurred.
Our supporting staff has been notified of this error and will address the issue shortly.
We apologize for the inconvenience.
Please try clicking your browsers 'back' button or try reloading the home page.
If you continue to receive this message, please try again in a little while.
Thank you for your patience.

and my site stop working after deleting the plugins site start working.
and if plugins not give this error then its show invalid key string.

Hi,

Can you please create a ticket mentioning the problem you are facing?

You can create a ticket by Singing to your nopStation account and going to the My Ticket area.

We will resolve the issue asap.

Thanks,
Team nopStation