Warning "coverpoint is not dumped to the coverage database because all bins are empty""

I believe your ignore_bins has ignored all the bins that you've tried to cover.  If you have crosses it's not obvious to get the exact bins you want ignored/illegal.  I can send you a short presentation on ignore/illegal bins if you want.  tmackett@cadence.com

Notice this simple example:

> irun ignore_bins.sv -coverage U -line -covoverwrite

---File: ignore_bins.sv

 module random_bins;

integer a;
  
covergroup cg1;
c1: coverpoint a {
    bins low = {[1:5]};
    bins high = {[6:10]};
    ignore_bins prime = {[1:10]};   <--- notice this eiliminates all possible values
 }
endgroup

cg1 cover_inst = new ();

initial
begin
   repeat (10) begin
   a = $urandom_range(10,1);
   cover_inst.sample();
  end // for
end  // initial

endmodule
------------------------

 ncsim: *W,WCOVPT: ./illegal_bins.sv:6: The coverpoint 'random_bins.cover_inst.c1' is not dumped to the coverage database because all bins are empty.