If a new firmware is available for the CCU2, then you should also update it, of course. But this has nothing to do with the interaction between the CCU and Homey. By updating the firmware of the CCU bugs are fixed, processes are optimized, new devices are supported. As with other devices too.
It seems like everything is configured correctly (because you are able to add devices), but anyway here are some info about the configuration of the CCU and the Homey Homematic App.
Info from the CCU installation description on GitHub
In the firewall of the CCU, ports 2121 (HTTP), 2122 (HTTPS), 1883 (MQTT) and 8883 (Secure MQTT) must be unblocked, depending on the use case:
These are the settings of the Homey Homematic App I have (I guess port 2121 in you setting will also work):
→ Save changes
→ Show Stored Bridges (then you will see a serial no. and the IP address of the CCU)
Yes, this is correct. So you can add your device.
