post of March 31 2020. "Before you used to only be able to do a 90 day online report from 15 days before down until 7 days BEFORE your actual due date. They evidently did an update to the system on March 20th and now the window of opportunity is from 15 days before right down until your actual due date".
If you do not pass the first page and get the little "contact your local immigration office" message, then there is a data miss-match and the only cure seems to be to do it in person.