@Avieck 

Hey

You will need to setup port forwarding (also called Virtual Servers) under NAT on the router.   This will allow the connection from external to be forwarded onto the device you require.

However you will need to know the port numbers and protocols used for each device.

More info can be found in the manual under section 2.2

https://static.tp-link.com/2020/202007/20200730/1910012780_TL-R605&TL-ER7206(UN)1.0_UG.pdf

  @Avieck 

You may check your NVR IP address, is it still using the same IP as when it work with old router?

Then go to ER7206 webinterface->Transmission->Routing->Port forwarding page, open the port for the NVR.

  @Avieck 

Thanks guys for your answers

All the inside IP's and Ports are configured in the virtual server.

I didn't mean the devices static IP, but the external static IP ftom my ISP.

I'm still using my ISP's router as the WAN modem.

  @Avieck 

Depending on your ISP modem router, you may also need to setup forwarding on this also.  

Some ISP devices can switch to Modem Only Mode, if so that would help.  If your ISP device cant do that, then you will need to forward the ports from the ISP Router to the OMADA router first..

Ok example.   Say we want our NVR external and the NVR uses ports 12345-12350

On the ISP router forward ports   12345-12350  to ports  12345-1235 on the Omada router.

On the Omada router forward ports   12345-12350   to the NVR

That help any?