Your welcome... Windows DNS implementation can be quite complicated with multiple interfaces as each interface as a different dns setup. On linux, or unix its much easier .... dns parameters are always in /etc/hosts.....
If this ever happens again you can try to hard code the ip address for your 3cx platform in:
c:/windows/system32/drivers/etc/host using notepad you can just add your platform to the host table.
Restart your web browser, as IE, Mozilla, and Chrome all look at the hosts table before making a DNS request.
Otherwise nslookup should tell you....with ping and traceroute.exe
Cheers and Have a good weekend.