It's also my understanding that even if the SEC had questions about the financials recently submitted, they don't have to publish those communications until the issue is concluded. Right? So shareholders are always in the dark right up to the time of a suspension?
The SEC usually, though not invariably, sends delinquency letters to registrants behind with their filings. I don't know how late the company has to be to get one. It's expected to respond to the letter. If it doesn't, then the SEC may start revocation proceedings anytime between a few months and a year or more.
Naturally the company is free to inform shareholders of receipt of the delinquency letter, but I don't think I've ever seen one do that.