I initially chose to mail in my state tax return. Can I choose instead to file electronically?

If your federal was efiled and accepted you can try to efile state now.  Click on Add a State to let you back into your retun.

How to file state after federal

https://ttlc.intuit.com/community/e-file/help/how-do-i-e-file-my-state-after-i-already-filed-my-federal/00/26811