If they believe that these Imams are knowledgeable and know, there is no sin on them in sha Allah,

my friend’s husband sold his house after he converted to islam because he found out that it is haram. Then he looked for islamic banking housing and now they bought a house with islamic banking thinking that’s halal because the imams are saying that it is permissible. So will they be held accountable for that sin or not since they are following the imams fatwa?