Strange DNS behavior

[Chris Maness]

I have been running my own DNS for years with glue records and the whole
nine yards.  A couple of days ago (without warning) my DNS server stopped
resolving requests external to my local network.  If I portscan my server
from outside my local network, I see that TCP port 53 is open.  I can use
dig to resolve any host on that server as long as it is local, but if I try
to to use dig from a remote host.  It just times out.  I thought I might
have been hacked or something, but it does not appear that the named.conf
file has been changed since 2015 (according to the stamp).

Any suggestions as to what could be the issue?

Thanks,
Chris Maness