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.