Lee
The one month starts from the date of the Decision Letter and you can make a Late request up to 13 months after this date providing you are able to provide Good Cause for the request being late.
I think it is reasonable to assume that at least in the next few weeks there will be additional delays in the system until the situation settles, of course, this assumes that no additional restrictions on workers are made.
Gordon
Nothing on this board constitutes legal advice - always consult a professional about specific problems