Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/20319b41da73f286f09bb859b5d9f32e.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563