Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/2b5e2e894cb7417b0ad24884c95d04de.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563