Fidelity NetBenefits - HTTP-Status 400 (Bad Request)

I am unable to download Balance/Transactions from my Fidelity NetBenefits account.  The official position of their "Electronics Support Services" group is that they ONLY support select Quicken "products" no others including GnuCash.  Based solely upon other comments from Internet searches, I think the "problem" is one or more of the "Application Options".  I did find an old comment that said that the "appver" had to be "1700".  A later comment on MoneyDance said the "appver" now has to be "1900".  Unfortunately, neither of those values worked for me with GnuCash 2.6.3.  Does anyone know ALL of the various options for Fidelity NetBenefits?  I have no difficulty with any other financial institutions.