That's not working for me. What version of macOS are you on Matt? I'm on the latest, 10.13.2, and I'm noticing more and more crashes and problems lately in applications other than TextMate. Perhaps there is a change in 10.13.2 that prevents those buttons from becoming active.
I'm able to do Find All, and when I enter text in the Replace box I see that text being (potentially) replaced in the displayed search results, and the Replace All button is active. But Replace and Replace & Find are always grayed out.
I've had to resort to a slow process like clicking on each result and doing a paste for each one that I want to replace. Kind of a drag when I need it.
--ErikN