This typically happens if you are a brand new seller, or if you’re using the “New Seller Experience”.
If you are using the new seller experience, you will need to switch back to the old experience.
To switch back, all you need to do is click “Go back to the original” at the bottom of the page inside your seller central.
Then you can go ahead and try the ASIN again in the old experience. If you find it still doesn’t work or if you have any questions please don’t hesitate to reach out to our friendly support.