Brp lost and found

Hi,
The query is for BRP lost and found i made a complaint and filled the form paid fee every thing is done but they are asking for supporting documents and also provided link but ut doesn’t work it shows a blank page when I open it it’s my husband BRP which was lost but later i found and also for constent check we live in rented flat and he doesn’t have any bank account so no reason to fill in that form? Also let me know what does it mean by supporting documents? Have anyone applied for replacement brp within uk? Please let me know the procedure. Thank you