Can you access the Web Administration Interface of the Nucleus by typing its IP address in a web browser, or by typing http://Nucleus/ into the browser?
If not, can you attach a monitor or a TV to the HDMI connector of the Nucleus and post a photo of any messages that appear on the screen when the Nucleus is rebotted?
Welcome to the forum. I am seeing your Nucleus as online earlier today, have you been able to access it since your post? If you wish to confirm that it is booting up properly, the HDMI test would be a great way to verify, as @Geoff_Coupe mentioned. Also, please note the correct web address, the one you posted has no affiliation to Roon.