Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/653c6b47d0a0830550f8d5e221e0e7f2.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563