I have other places looks perfectly, but anywhere where I have these pages, none show buttons "next" and not properly output the total pages, but the "json" is correct.
the path are correct, none error.
require "../include/gridconexion.php";

include("../../lib/phpgrid-full-v1.5.2/lib/inc/jqgrid_dist.php");

// you can customize your own columns …

$col = array();

$col["title"] = "Id"; // caption of column

$col["name"] = "IdProducto"; // grid column name, must be exactly same as returned column-name from sql (tablefield or field-alias)
$col["editable"] = false;
$col["viewable"] = false;
$col["width"] = "6";
$col["align"] = "center";
$cols[] = $col;

$col = array();
$col["title"] = "Referencia";
$col["name"] = "Referencia";
$col["width"] = "15";
$col["sortable"] = false; // this column is not sortable
$col["search"] = true; // this column is not searchable
$col["editable"] = true;
$cols[] = $col;

$col = array();
$col["title"] = "Marcas";
$col["name"] = "Marcas";
$col["width"] = "15";
$col["sortable"] = true; // this column is not sortable
$col["search"] = true; // this column is not searchable
$col["editable"] = true;
$cols[] = $col;

$col = array();
$col["title"] = "Submarcas";
$col["name"] = "Submarcas";
$col["width"] = "15";
$col["sortable"] = true; // this column is not sortable
$col["search"] = true; // this column is not searchable
$col["editable"] = true;
$cols[] = $col;

$col = array();
$col["title"] = "Descripcion";
$col["name"] = "Descripcion";
$col["width"] = "50";
$col["sortable"] = true; // this column is not sortable
$col["search"] = true; // this column is not searchable
$col["editable"] = true;
$cols[] = $col;

$col = array();
$col["title"] = "EAN13";
$col["name"] = "EAN13";
$col["width"] = "20";
$col["sortable"] = true; // this column is not sortable
$col["search"] = true; // this column is not searchable
$col["editable"] = true;

$cols[] = $col;

$col = array();
$col["title"] = "EAN14";
$col["name"] = "EAN14";
$col["width"] = "20";
$col["sortable"] = true; // this column is not sortable
$col["search"] = true; // this column is not searchable
$col["editable"] = true;
$col = array();
…

$g = new jqgrid();

$grid["rowNum"] = 20; // by default 20

$grid["sortname"] = 'IdProducto'; // by default sort grid by this field

$grid["sortorder"] = "desc"; // ASC or DESC

$grid["caption"] = "Articulos"; // caption of grid

$grid["autowidth"] = true; // expand grid to screen width

$grid["multiselect"] = false; // allow you to multi-select through checkboxes

$grid["height"] = "490";

$grid["altRows"] = true;

$grid["altclass"] = "myAltRowClass";

$grid["export"] = array("format"=>"xls",
"filename"=>"articulos",
"heading"=>"Export to Excel Test",
"range"=>"filtered");

$g->set_options($grid);

$g->set_actions(array(

"add"=>true, // allow/disallow add

"edit"=>true, // allow/disallow edit

"delete"=>true, // allow/disallow delete

"rowactions"=>true, // show/hide row wise edit/del/save option

"export"=>true, // show/hide export to excel option

"autofilter" => true, // show/hide autofilter for search

"search" => "advance" // show single/multi field search condition (e.g. simple or advance)

)

);

// you can provide custom SQL query to display data

$g->select_command = "SELECT * from articulos_almacen";

// this db table will be used for add,edit,delete

$g->table = "articulos_almacen";

// pass the cooked columns to grid

$g->set_columns($cols);

//generate grid output, with unique grid name as 'list1'

$out = $g->render("list1");
session_start();