It seems that underscores in block name isn’t passing though.
So, textarea_block as a block name is not working, instead use a name without underscores, something like textareablock.
Try this:
if( function_exists('acf_register_block') ) {
acf_register_block(array(
'name' => 'textareablock',
'key' => 'textarea_block',
'title' => __('textarea'),
'description' => __('A custom pixel block.'),
'render_callback' => 'textarea_block_render_callback',
'category' => 'formatting',
'mode' => 'edit', // 'preview',
'icon' => 'admin-comments',
'keywords' => array( 'flexible', 'quote' ),
));
}
register_field_group(array (
'key' => 'textarea',
'title' => 'Text Area',
'fields' => array(
array(
'key' => 'textarea_title',
'name' => 'textarea_title',
'label' => 'Section Title',
'instructions' => '',
'type' => 'text',
),
array(
'key' => 'textarea_text',
'name' => 'textarea_text',
'label' => 'Text',
'instructions' => '',
'type' => 'wysiwyg',
),
),
'location' => array (
array (
array (
'param' => 'block',
'operator' => '==',
'value' => 'acf/textareablock'
),
),
),
));
P.S. I’ve added 'mode'=> 'edit' to start ACF block in edit more.
