Apparently this is an AR requirement. The state return can be filed electronically ONLY if efiled along with the federal return. I'm attaching a page I found when researching your question on the AR DOR website.
Since you didn't efile your AR return at the same time that you efiled your federal return, you'll need to print and mail your AR return. So sorry!
*** I am NOT a tax expert. I am a seasoned TurboTax user, and volunteer to provide assistance to TT users. Nothing I post is to be considered TAX ADVICE; I bear no legal liability for responses.***