Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/c70c6a2b4a61060944122fc51c8974ab.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563