A bug in Opera. Seems many people at the Opera forum are having this problem. You type in a web address or a search term in the URL address bar and hit enter and… nothing. The words go gray and that’s it. It happens randomly.
So what I do when it happens, I just high-lite the web address or search term I just typed in, then I right-click on it and then Copy.
Then I right-click again and click on Paste and search (or go). It works for me. Hopefully, the next Opera update will fix this problem permanently.