Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/2c504e217e60f3e7988b3fb4af8b14fb.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563