Try another browser to rule out a browser issue.
Have you done a lot of research today? If I recall correctly, there are limits to the number of searches you can do in a day, though I forget what happens when you get to that limit, whether there is an error message.
It might be worth trying the same search through the app.
Or, if you have more than one account, try the search using a different account. If the account is not used for selling, you may have to enable seller hub first, though.
