Hello  @jeff9988 

When did port forwarding for multiple camera, and you should define different External ports for camera but the Internal ports are always  2020/554, e.g.

1st Camera: External Port 2020 & 554 ;   Internal port: 2020 & 554 

2nd Camera: External port 2021 & 555  ; Internal Port : 2020&554 

• ONVIF Service Port: 2020
• RTSP Service Port: 554

• RTSP URL : rtsp:// camera IP Address:554/stream1 
• ONVIF URL: http://camera IP Address:2020/onvif/device_service
• Note for remote control, change cammera IP to router’s WAN IP or public IP

If that's does not work on the second camera, please check if you could access 2nd camera in the local network? If you could access the 2nd camera locally, that could be something wrong with port forwarding, you could share the model of router &  network topology and photo of port forwarding settings here for us to look into that further. 

 Hello  @jeff9988 

I think you are right, mostly likely the NAS surveillance software use default port 554 for RTSP streaming, so the software leads to the same camera Live view 

I suggest reaching NAS support and see if they have more suggestion with setting up multiple ONVIF connections to multiple cameras remotely. 

You could also consider using an RTSP software like VLC Player and to set up multiple RTSP streams and view  cameras remotely. 

Can I know the version of the NAS surveillance software, or you could share a link of the software by private message. 

What URL do you use to access the first and second camera? You may share via private message.