Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/1f0b2dfe8704dae3fe8d0b5190bd6e28.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563