I setup vital pbx internally on my network using hyper-v. I am currently trying to make sure everything works internnal. I setup a certificate with Letsencrypt. The certificate shows valid and set me internal DNS to route to that IP. When I go to the site using the FQDN it works for a few minutes and then it gives me an error connecting. When I have this issue I can try it from multiple PCs on my network and it won’t work. It will eventually start working again after a minute or two. When it isn’t working with the FQDN it still works with the direct IP address. I turned off the firewall on the vitalPBX (it is only accessible internally on my network) and have check the apache access logs and I don’t see anything that shows these errors.
I believe I found the issue. I traced the data with wireshark and when the issue happened I noticed the data was not going to the local IP. I had secure dns enabled on the browser. I don’t know why it worked sometimes and not other times? I disabled secure dns and it seems to be working.