Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/f5211e8f3e0930b78b2a2bc90089784f.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563