I made a custom module for seller management. It is working fine on local server but not on the live server. I am getting an error in loading my block.

Controller.php
--------------

```
protected function _initAction()
{
    $this->loadLayout()
            ->_setActiveMenu('managesellers/managesellers')
            ->_addBreadcrumb(Mage::helper('adminhtml')->__('Seller Manager'), Mage::helper('adminhtml')->__('Seller Manager'))
            ->_addContent($this->getLayout()->createBlock('managesellers/adminhtml_managesellers'));
    return $this;
}

public function indexAction()
{
    $this->_initAction()
            ->renderLayout();
}

```

I am getting an error in the `addContent()` method but only on the live server. It works fine on my localhost.

> 
> ERROR: Fatal error: Uncaught TypeError: Argument 1 passed to
>  Mage\_Adminhtml\_Controller\_Action::\_addContent() must be an instance of
>  Mage\_Core\_Block\_Abstract, boolean given
> 
> 
> 

Need your assistance to rectify this.

Edit: Added the code of config.xml and the block class.

Config.xml
----------

```
<config>
<modules>
    <COC_ManageSellers>
        <version>0.1.0</version>    <!-- Version of module -->
    </COC_ManageSellers>
</modules>
<frontend>
    <routers>
        <admin>
            <use>standard</use>
            <args>
                <module>COC_ManageSellers</module>
                <frontName>managesellers</frontName>  <!-- This is the URL of the module. i.e www.clickoncare.com/index.php/managesellers -->
            </args>
        </admin>
    </routers>
</frontend>

<adminhtml>

    <menu>
        <managesellers module="managesellers">
            <title>Manage Sellers</title>
            <sort_order>120</sort_order>
            <action>managesellers</action>
        </managesellers>
    </menu>     
    <acl>
        <resources>
            <all>
                <title>Allow Everything</title>
            </all>
            <admin>
                <children>
                    <managesellers>
                        <title>Manage Seller</title>
                        <sort_order>10</sort_order>

                    </managesellers>
                </children>
            </admin>
        </resources>
    </acl>
</adminhtml>

<global>
    <blocks>
        <managesellers>
            <class>COC_ManageSellers_Block</class>
        </managesellers>

    </blocks>
    <helpers>
        <managesellers>
            <class>COC_ManageSellers_Helper</class> 
        </managesellers>
    </helpers>

    <models>
     <managesellers>
        <class>COC_ManageSellers_Model</class>
        <resourceModel>managesellers_mysql4</resourceModel>
     </managesellers>
     <managesellers_mysql4>
        <class>COC_ManageSellers_Model_Mysql4</class>
        <entities>
           <managesellers>
              <table>managesellers</table>
           </managesellers>
        </entities>
     </managesellers_mysql4>
  </models>
  <resources>
     <managesellers_setup>
        <setup>
           <managesellers>COC_ManageSellers</managesellers>
           <class>COC_ManageSellers_Model_Resource_Setup</class>
        </setup>
        <connection>
           <use>core_setup</use>
        </connection>
     </managesellers_setup>
     <managesellers_write>
        <connection>
           <use>core_write</use>
        </connection>
     </managesellers_write>
     <managesellers_read>
        <connection>
           <use>core_read</use>
        </connection>
     </managesellers_read>
  </resources>

</global>

```

Block Class
-----------

```
  public function __construct()
  {
     $this->_controller = 'adminhtml_managesellers';
     $this->_blockGroup = 'managesellers';
     $this->_headerText = Mage::helper('managesellers')->__('Seller Manager');
     parent::__construct();
  }

```