Can't move items with a User field

I’m trying to move items from one board to another, and it has a user field, with data in it about which user an item is assigned to, I’m trying to move to a sprint layout board, which has an assignee field.

Obviously I’ve tried to update the source board to ensure the column name and type match, but whatever I do, creating a new temporary user column, renaming all day, I cannot get the user data to transfer from one board to another.

IS this is a known issue? Something special about me?

Maybe you need to invite all users from previous board to new!

Thanks, it’s a good thought but they are all invited, and I’m one of the people…