Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/3ba77e6459b2d1fb4293fffe7e0d3d19.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563