Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/a8e2e7d5792c2071fa3b1cc649e8f3ee.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563