Hold down Select as you're turning on the device (press it down before pressing the Power button, and keep it held until you see the Luma settings menu). Do the same with Start and you should boot into Hourglass9. If you still don't see this, then A9LH may not have been successfully installed. Could you show me the current contents of your a9lh folder? Also you can delete the .7z file now.
This is normal behaviour that sometimes occurs on 2.1.0 when using a 2DS, iirc. It will be fixed when you restore your NAND backup.