NVR on Google Wifi; Can't access outside of local network

[toga434]

I can't access my NVR main menu/settings/etc outside of my local network, via DDNS URL and port.
But I can access the NVR and IP cameras on the local network via the Amcrest View app.

Here's the setup:

Verizon Router (WiFi disabled) --> (main) Google WiFi puck --> (downstream) Google WiFi puck --> Amcrest NVR and IP Cameras (WiFi and PoE)

NVR: Port 37776
IPCAM 1: Port 37777
IPCAM 2: Port 37777
PoECAM: Port 37771

DDNS is enabled

Google WiFi Port Forwarding enabled for the following (not sure if these are correct):
IPCAM 1: 37776 -> 37776 (TCP)
IPCAM 2: 888 -> 888 (TCP/UDP)
POE Cam: 37771 -> 37771 (TCP/UDP)

[WilliamA]

Double NAT issue. Connect the NVR to the fios router.