First of all you need to have a public WAN IP address provided by your ISP.

It is good too hear this topology work well in you case. Vivo Fibra <--- WR841ND <-- WA830RE <-- WA830RE But using a second repeater is not a good idea for many situations. It could be unstable and...

Use different channel among 1, 6, 11.

Is there anything changed in your network before these issues happened? Check whether there is a loop or not. A loop can lead to broadcast storm and put down the network.

It does behave as @coca koala described... More: If we don't click the logout button in the menu before closing the browser, it keeps the login session and won't allow other users to log in for 5...

As @Vivian said, you need to change the camera's IP address to the same subnet as the TD-W9980