Yes, you can still e-file if you have printed your tax return. 

Make sure you chose "e-file" in Step 3 of Filing.  

However, you cannot still e-file if you have printed and mailed your tax return. 

I have printed, but have not mailed my return. But I cannot find the tab anywhere to review my filing options to switch back to efile. It only says “Ready to Mail” and gives me the option to download/print my return.

me too please help