advice pls,urgent!

i applied for my residence card about 7 months ago on the basis of married spouse,having submitted all the documents required including our mariage certificate. However,i got a letter from the home office which said that i had applied on the basis of unmarried couple. I am a non eu and my wife is an eu citizen ,we married over a year ago and then applied for a residence card.The letter asked me to send my paspport with my wifes,evidence of my wife excersising treaty right,and loads of other documents require from unmarried couple applicant.e.g "letter to show that our relationship is kin to marrige." could you please advice me on how to go about this? I have been given 21 days to reply. thank you so much.

HO might have lost the marriage certificate,if that is the case get a copy from where you married and send it to them with a cover letter

thank you trouble,but they not only asking for the marriage certificate but also our passports which we had already sent to them.Is it possible that they lost all the documents sent to them?Has anyone had the same problem in the past? thank you!