Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/b11735f3d3b2f7e95d4c6ff05c68a159.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563