DnB Unmatched Records Logic (Salesforce Integration)

Does anyone have experience with how to get passed the unmatched records? Ie: Duns Numbers

I've been talking with DnB and they don't seem to have a solution- we currently have 1300 unmatched records. No assigned Duns number, they've mentioned I need to add more information into the fields but even some accounts with full records aren't matching.

Thank you so much.

Kind regards,

Lauren