Trouble with new security protocols

I'm having trouble getting to a web site I haven't had trouble with in the past:  treasurydirect.gov

I've tried 4 different browsers: Firefox, Edge, Chrome, IE.  All fail.

An error page stating the following comes up (from Firefox):

Secure Connection Failed
The connection to the server was reset while the page was loading.
    The page you are trying to view cannot be shown because the authenticity of the received data could not be verified.
    Please contact the website owners to inform them of this problem.

I have contacted TreasuryDirect by phone.  They indicated that I am not alone in experiencing this difficulty.  They indicated a recent update to their security protocols and are considering whether that change might be the problem.  They did indicate that they thought the problem was isolated to a small set of Win10 systems. 

I'm on Win10.  The OS is up-to-date as are all of the browers being used.  It behaves the same on both my tablet and my desktop computer (both on up-to-date Win10 systems).  I'm on Gen5.  I called a friend who tried to access the site on a Win7 system with the Chrome browser and had the same problem.  That friend is also on Hughesnet (Gen 5).  This makes me wonder if it isn't a problem with this secure site's interaction with Hughesnet.

While I'd hope it wouldn't make any difference I've currently used up my allowance.  I don't think that was the case for my friend. 

fwiw: I've been able to access other sites with secure-predilictions : e.g. e-commerce sites & a set of other goverment sites.

Can any of you successfully get to this site?

Thanks for any insight you can provide.