Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/0b84f0a61a941049fd04d18b7103aac0.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563