https://engineering.gusto.com/how-ach-works-a-developer-pers... A good time to remind people that the USA's money-transfer system (aka: ACH) is a giant Rube-Goldberg machine involving FTP transfers of specially formatted files. So it sounds like the Fed's FTP server is down?? Or something like that?
Why wouldn't they use SFTP?
From what I've seen in other countries, you don't update protocols for this. You introduce better ones and kill the old ones once nobody used them for a while. Which might take longer than expected, because "free instant transfers" might be seen as cannibalizing the "slightly less slow expensive transfers" any given bank might have on offer.