Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/2184cd6c3d4c1d2577be1de61f33d117.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563