Amended return for 2018. I have completed the data, but TurboTax won't let me file it (it says federal return already filed).

I completed my initial 2018 fed and e-filed it.  Two hours later an additional 1099-R arrived in the mail.  So I immediately started and completed an "amended return."  Now TurboTax just sits there and says I've already filed.  Need a little help here.  TIA