Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/11ec97ce3d4b3f8c4c25bb37999f8969.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563