Vivado:Error-Ambiguous clk in event control
Your second if statement isn't controlled by reset_n, which makes it non-synthesizable. You probably meant something more like:

  always @(posedge clk or negedge reset_n) begin
    if (reset_n == 0) begin
      counter_debounce &lt;= 0;
    end else begin
      if (counter_debounce&gt;=100000000) begin
        counter_debounce &lt;= 0;
      end else begin
        counter_debounce &lt;= counter_debounce + 1;
      end
    end
  end