I changed to a new router

The easiest way would be setting the network name(SSID) and password to be the same as your older router. The remote and the monitor would work automatically without any changes.
If you can’t do that, you can factory reset the devices and add them to your new router again just like how you did it the first time by clicking the “+” button in “My Devices” screen and follow the first time setup instructions.

Here’s how to factory reset for the remote.

I have GDB Remote 2.0, how do I factory reset the device?

Here’s how to factory reset for the monitor.

Factory reset for GDB Monitor