Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/7d50ad786ec8d8f664a2df78cc4659e4.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563