Unable to access ".mil" websites on home WiFi

I have seen other post regarding this issue, but there are no solutions posted. Websites that end in ".mil" will not load on my home Xfinity WiFi, and the resulting error message reads "DNS_PROBE_FINISHED_NXDOMAIN." This problem is specific to WiFi, as I'm able to access the sites upon turning WiFi off on my phone. Of particular importance is https://milconnect.dmdc.osd.mil, which worked on home WiFi a matter of months ago. I submitted a ticket yesterday, and the response given was "there is no Advanced Security block related to the reported website," but from what I've read on this forum, as well as on other chat platforms, there is an inherent problem with Xfinity WiFi and these sites. Please advise and assist. Thank you.