That screenshot you posted of trying to reach the Web Administration page of the Nucleus and got a screen with “Failed to load device state (status: 0). Please refresh” - that can be a symptom that the M.2 SSD holding the Roon OS and Roon has failed. See this report in the forum:
Is your Nucleus still within its 2-year warranty? And did you purchase it from a dealer or direct from Roon Labs?
@benjamin - please advise on the next steps. Thanks.