See https://home.dotgov.gov/2018/10/1/doing-the-2-step/#how-do-i-set-up-2-step-verification
Why can I not access systems within my domain, but people
outside can?
To speed up the entire DNS process, name servers will
temporarily store IP addresses that they have found. This means
that if someone in the office next to you visits
www.dotgov.gov
and then you visit the site shortly afterwards, you receive the
IP address from the local, temporary storage rather than
through the root servers. If you or your ISP's local name
server is not "expiring" this temporary storage
(called a cache), you could be getting incorrect IP addresses
while people connected through different ISPs are getting the
correct information. Please contact your ISP or local technical
support for assistance.
Where do I look for the authoritative .gov zone data?
The
root servers (e.g., a.root-server.net - j.root-server.net) are
the authoritative source of .gov information that is
"live" on the Internet.
What are the hours of operations for the Registration Help
Desk?
The
Registration Help Desk is open on U.S. government working days
from 9 a.m. to 5 p.m. Eastern and 24/7 for
emergencies.