As his PR date isn't written on his DCPR, you will have to ask your husband what date he told UKVI that he had reached the EU's PR. The EUs PR isn't granted, as the EU gives PR automatically.
For a DCPR to be able to apply for British citizenship, he had to provide the documents to UKVI to prove that PR date that he claimed he had. If they agree they issue a DCPR, which they did.
As I said above, if he is still within 2 years of the date of his PR, then it looks like UVKI made an error and all you needed was his DCPR. I have no idea if an AR will work as you were refused on two things.
If you are going to apply again, then you have to treat it as a new application. As the date your husband achieved PR isn't on his DCPR, you will have to ask your husband what date he told UKVI, to see if it is more that 2 years. If it is, provide the DCPR and the proof that he hasn't resided outside the UK for two years since he got PR. If you wanted to be sure, you could always send his DCPR and the proof that he has remained in the UK.
PR is lost after two years outside the UK and then they start again with exercising treaty rights for 5 years to PR. This is why PR for more than two years needs that proof that they have not lost PR.