The MD Form 511 is available for efile at this time. We have seen MD 511 forms being electronically filed for s corporations.  The update released this morning removed print restrictions on the MD 511 after receiving approval from the State of MD and should not impact efile.    

Can you take a look at the Form 511 in the software and confirm that the s corporation box is being checked here please?  I am trying to understand why you are specifically having an issue as an s corporation filing the MD 511.