Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/b7103d629b850ccf7c2c7343da3e2b5f.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563