It looks like you have previously dd'd a hybrid boot image to this usb stick so grub can not be installed there due to the presense of multiple partition tables. You will need to use wipefs or similar to remove the non dos partition tables.
** Changed in: grub-installer (Ubuntu) Status: New => Invalid -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1775107 Title: Edubuntu failed to install on 16GB USB drive. To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/grub-installer/+bug/1775107/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs