I've recently run into an odd issue for one of my offline SEPM servers, whereby manually running the "Download LiveUpdate Content" option results in a failed LiveUpdate attempt. The return code is 4, and the error occurs very quickly, usually within 10 seconds or so. Event Viewer for SEPM only shows "Content download to the server failed.", with an Event ID of 7201. As far as I can tell, this particular SEPM is simply unable to detect or cannot access the C:\inetpub\wwwroot\clu-prod folder that it usually draws its updates from.
This is 1 of the SEPM servers that I handle, and all of them use the same set of updates downloaded off an online-connected Liveupdate server. No other SEPM server has the same error. I've checked the settings for SEPM itself, and the issue started with one of its automatic LiveUpdate processes (and at off-work hours for my department, even), so I'd like to ask what are some of the possible common causes for this issue.