Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/1b97f407542b918a9a6ce25142f7f435.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563