Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/2ea7e174f1cd3d3a09c0fe2f14202069.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563