Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/53d5d20f2b0d1e5e3f9d05663b6d2635.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563