Seemed I've been hit as well but after updating to EmuNand 9.5, I can connect again.
What flashcard were you using (Gateway or Sky3DS etc): Gateway3DS
What game were you playing: Theatrhythm Final Fantasy Curtain Call (E)
What was your sysNAND firmware version when playing: 4.5.0.4E
What was your emuNAND firmware version when playing: 9.4.0-21E
Were you using a .CIA or a .3DZ: 3DZ If you were using a .3DZ file, from what game was the header you were you using: Super Mario 3D Land (E)
Header Name: CTR-AREP
If you were using a .3DZ file, was the header public or private: private
Can you visit other online Nintendo services such as eShop and Miiverse: eShop seems to work, but was stuck on the loading screen for ~5 mins. Miiverse works
Does that ban apply to just that game or every online game you try: I don't have any other game with online capability right now
Any Additional info:Theatrhythm DLC installed via CIA. Restarting and updating to 9.5 solved the issue.