Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/f2e291c333abbcda4fe5e8ec94b019de.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563