New modem, cant access NAS services from outside

[Didam]

I had a working setup: diskstation with reverse proxy (multiple sub-domains), my router, cable modem. I had port forwarding to a custom port on the modem, then on my router from the custom port to the NAS:443.
I got a new cable modem today. I setup a port forwarding rule on it (custom port to my router:custom port). I get an open port status from Open Port Check Tool - Test Port Forwarding on Your Router . If I remove the port forwarding on my router, the port check says the port is closed, so it seems like things are fine at least to my router.
But I cannot access my services... what obvious setting am I missing? I have not changed any settings on my router or the NAS from it's working condition.

 

[Rusty]

I'm wondering if the old modem had some "loopback" rule that made this additional port forward unnecessary.

Most likely that was the case. If you recall I did ask about loopback support in my initial question. Using FQDN name inside LAN can fail if that feature is not supported, or in your case blocked.

Glad you got it going in the end.