Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/ee6744019f2a1ba7210f4b67a7d58cb3.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563