Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/725d7760f9f6a6d8d51a3a36b111c708.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563