Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/2bc3a550516ee9fa0ec2bb8c105db6a7.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563