I filed my federal taxes for the year, but I had to wait until the 31st of January to file my state taxes. It's now saying I'm not allowed to file more than one form?

I filed on the 28th, and sent in my federal stuff and planned to do my state ones on the 31st or 1st. I'm currently trying to send in the state taxes but it won't allow me, saying I'm not allowed to file more than one form. How am I supposed to get my state taxes filed?