The 2015 e-file business rules included reject code R0000-198:
This return is ineligible to be filed electronically.
The IRS may issue this reject at any time. A return can receive this reject the first time it is transmitted or subsequent to fixing a different reject. Or, an amended return may receive this reject.
The IRS does not go into detail regarding why a return may get this reject nor how to resolve it, only noting that the Modernized e-File system "is rejecting returns based on characteristics that have been deemed highly suspicious." The only option for a return such as this is to paper file it.
If you have any questions, contact IRS Practitioner Priority Service at 866.860.4259.