Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/d4b6426091b1d561dccd9b71bf3a5f74.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563