Could it be that you have set the notifications and alarm detection to unlimited?
It is advisable to set these a little lower, because the push messages go through the IOS and Google servers.
They have a policy that if too many notifications come in from a device, it will be banned for a while.
As soon as your device is allowed again and more notifications come in, you will be blocked again.
It is also possible that the security settings in your modem are too high.
You can always turn on the UPNP (universal plag and play) function for that device and in some modems this is a general setting.
You can also try to forward your camera over port 80 with a UDP protocol.
It is advisable not to use routers, because if they are not set up correctly, things can go wrong in your network.
If you do use routers, configure them as switches with DHCP turned off.
How to do this can be found in the manual of your modem/router or ask your internet service provider.