If your firmware was 11.2.0-35E, then you might have done the CTRNAND transfer with the 2.1.0-3U file on accident when you downgraded, then updated via CTRNAND Transfer to 9.2.0-20U afterward, because you thought your region might be NA. In this case, I think you will need to:
1. downgrade CTRNAND to 2.1.0-3U
2. Uninstall A9LH
3. CTRNAND Transfer to 2.1.0-3E
4. Reinstall A9LH
5. CTRNAND Transfer update to 9.2.0-20E.
If this doesn't work, then I don't have a clue what else to suggest. You might need to buy a used 2DS from a store and install A9LH on that instead.