Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/90da6d08b4a22291b00346c1fef7e4f4.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563