As I kind of eluded to in the forum sticky, we're having trouble because we have over 10,000 users requesting SSL certificates at the same time from letsencrypt and they do not let us do that. Unfortunately, until the queue clears out a bit you may actually have tried to get a certificate when we reached our hourly limit, but then the command ran again later and it worked. Since this is a limit of letsencrypt I can't do anything to force it, but if we're just patient over the next few weeks things will settle out. Letsencrypt certificates are automatically renewed, but I think that they will start getting spaced further and further apart once the system settles down.