Debz
I think it highly unlikely that you can address this.
The absolute limit for appeals is 13 months, I am afraid that your not being aware of the requirements would not be reason for the DWP to re-visit the Decision.
You could speak to a trained advisor to see whether they can think of any way to back date the claim, but I would be surprised if they do not agree with the above, do an internet search for "welfare advice" with your postcode, town, or county.
Gordon
Nothing on this board constitutes legal advice - always consult a professional about specific problems 
