I have Seo Suite extension installed and sorting does not work in magento.

Please do the following:

1) Open app/code/local/MageWorx/SeoSuite/Block/Catalog/Product/List/Toolbar.php

2) Replace 
extends Mage_Catalog_Block_Product_List_Toolbar
with
extends Amasty_Sorting_Block_Catalog_Product_List_Toolbar