Amasty Coupons

1. Open app/code/community/Amasty/Coupons/Block/Rewrite/Cart/Coupon.php and find the following code:

   protected function _toHtml()
   {
       $this->setTemplate('amcoupon/checkout/cart/coupon.phtml');
       return parent::_toHtml();
   }
   

2. Replace it with:

   protected function _toHtml()
   {
       $this->setTemplate('amcoupon/checkout/cart/coupon.phtml');
       if ('firecheckout' === $this->getRequest()->getRouteName()) {
           $this->setTemplate('tm/firecheckout/amcoupon/checkout/cart/coupon.phtml');
       }
       return parent::_toHtml();
   }
   

   and save the file.

3. Disable compilation mode and clear Magento cache.