Remote build iOS "Connection timed out" or "Could not resolve hostname" after router and ISP change

After changing ISP and router, I am no longer able to remote build for iOS. Initially, the build failed with “Connection timed out” every time. After messing with the router’s firewall settings (enabling IP passthrough, and/or attempting port forwarding) I also occasionally get “Could not resolve hostname” similar to question found here: SSH Remote Build Failed

This is a blueprint-only project. The change was from Xfinity with an old personal router, to ATT with router model BGW320. Other than the new ISP and router, no changes were made between the most recent successful build and now. I have double checked the IP address on the mac side hasn’t changed, and have attempted setting up a new SSH key using the mac’s name instead, without success.

Anyone have the same problem? Any ideas? Any thoughts on connecting SSH via another port, or some other workaround?