That person should start with the assumption they haven't been misclassified and eliminate the possibility that a device on their network is compromised.
(Author here.) That’s missing from the article. But I have logs of the network. There’s nothing out of the ordinary. “I don’t know what I did wrong,” as I started the article, means “I’ve checked logs and such and there’s no indication of anything wrong on my end.”
That person should start with the assumption they haven't been misclassified and eliminate the possibility that a device on their network is compromised.