Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/5b2aa0fd1f00f6d93a26cb34537adb12.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563