Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/b2aacd1d24b4067b3b8c00d988b7153d.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563