You probably have to file on paper this year, since the dependent already appears on a return.

A paper copy will need to be submitted this year.  

If you get an IPPIN for the taxpayer, then it will get accepted, but both people that claimed the kid will end up with a letter requesting proof that they are allowed to claim the dependent, so be prepared for a long refund wait, either way.

@rbynaker suggested your solution in another thread, he might have more details.  I would think it might take IRS a weekly cycle to update.  

https://accountants.intuit.com/community/lacerte-tax-discussions/discussion/resubmitting-rejected-re... 

Just had similar problem.  Dependent did not check the "check-box" to say he was a dependent on another person's tax return (i.e., the parents).  Dependent amended electronically on TT and I waited over a month with numerous, continuous rejections of parents' returns.  So apparently, the child's amended efiled return was not able 'reset' the 'trigger' in MeF (at least after one to one & 1/2 months).  Thus, we paper filed.

E-filed amended returns are processed the same way as paper-filed amended returns.  IRS is three months behind on processing both types. 

Lisa:

Thank yo so much for your Advice.

Your solution was exactly what we needed to get the tax return to E-File.

I do follow your Posts on other issues  as well

John