I do know Blender, and I would have recommended making sure that a keyframe existed in the portion of the animation you were isolating so that it didn’t export nothing…
and don’t be that guy, cpeppler! Nothing is more annoying for someone in the year 2026 who Googled this issue, found this thread, read it with eager anticipation, and got to the end to see “EDIT: Fixed it” with no explanation of how you fixed it! Always include a parenthetical of what you missed/what you did. For posterity!