First, the communication you received from tech support is incorrect.  The MD Form 511 is available for efile at this time.  We are currently seeing MD 511 forms being electronically filed for s corporations.  

Can you take a look at the Form 511 in the software and confirm that the s corporation box is being checked here please?

Not in specific answer to your question but Comptroller of MD has not approved 511 for printing yet.  You can e-file but not print (weird). Maybe there is something now that COT has us holding up everything.  This is getting nuts as it's August and we've been held up for months now. The Sept 15th deadline is fast approaching and will be a nightmare.........