Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/ecb950f1f75f1e7443b09079b8cd0ce5.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563