Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/ce5b3b1b0839a031b04b937e2f04cf00.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563