Strangely, Graphisoft has been cautioning against using a dynamic DNS service recently, even though throughout 13 they recommended it.
My guess is that they found that some people were not properly updating their DNS assignment, causing things to break and wasting tech support time.
This is the key: you MUST make sure that if you have a dynamic IP and using a dynamic DNS service such as the free dyndns.org - that you do at least one of these things (1) install and run their helper application which will report to their servers any time your external IP address changes, and/or (2) if your cable modem or router supports it, have it report any updated IP address back to the dynamic DNS server.
The installation of the helper app is described on the provider web site.
Dynamic update via your modem or router depends on which of the 100's of models you have. Attached is a screenshot for my Netgear router's page which "knows" about dyndns.org and will update things automatically even if no computers are on. The hostname is the free hostname that you request from dyndns.org. The username/password are your credentials for logging onto you dyndns.org account.
Cheers,
Karl
One of the forum moderators
AC 28 USA and earlier • macOS Sequoia 15.2, MacBook Pro M2 Max 12CPU/30GPU cores, 32GB