In some apps, the "Go", "Search", or similar button in the bottom right of the keyboard remains dimmed if you have entered text only using Braille Screen Input. You must type a character using the on-screen keyboard before you can activate the button.
For example, in the App Store, open the Search tab and type a search using only Braille Screen Input. Rotor out of BSI and find the "Search" button in the bottom right of your on-screen keyboard; it should be dimmed. If you hit a space, or any other character, on the keyboard and then delete that character, the button will work as expected.
This is not a problem in all apps, only some. It is also not a problem in only third-party apps; I've seen it in the App Store and Voice Dream Reader, for instance.