Boot-Repair:
Boot repair is the FREE simple tool used to repair common boot issue (MBR) on various of other Linux distro such as Debian, LinuxMint, Ubuntu and Windows version from Win 7 until Win 10. The software does not come by default in Ubuntu 18.04
This post guide user on how to load the Boot-Repair utilities tool from Ubuntu Live CD.
Step 1: Load the Ubuntu Live CD or Ubuntu bootable USB Flash drive. Select “Try Ubuntu” option when Ubuntu screen come up.
Step 2: Launch Terminal from Ubuntu Applications.
linuxref@pc-linuxref:~$ sudo add-apt-repository ppa:yannubuntu/boot-repair
[sudo] password for linuxref:
Simple tool to repair frequent boot problems.
Website: https://sourceforge.net/p/boot-repair/home
More info: https://launchpad.net/~yannubuntu/+archive/ubuntu/boot-repair
Press [ENTER] to continue or ctrl-c to cancel adding it
gpg: keyring `/tmp/tmprr6mm7p_/secring.gpg’ created
gpg: keyring `/tmp/tmprr6mm7p_/pubring.gpg’ created
gpg: requesting key 60D8DA0B from hkp server keyserver.ubuntu.com
gpg: /tmp/tmprr6mm7p_/trustdb.gpg: trustdb created
gpg: key 60D8DA0B: public key “Launchpad PPA for YannUbuntu” imported
gpg: Total number processed: 1
gpg: imported: 1 (RSA: 1)
OK
linuxref@pc-linuxref:~$ sudo apt-get update
Step 3: Install Boot-Repair via “apt-get”
linuxref@pc-linuxref:~$ sudo apt-get install boot-repair
Step 4: launch boot-repair from terminal, select “Recommended Repair”
linuxref@pc-linuxref:~$ boot-repair


It automatically find and fix the problem if found. User have option to select ‘NO’ if don’t want to post report to pastebin. After that, it will prompting with few message and summary of the finding.



Reboot your pc/laptop and make sure the Grub2 is working.
Conclusion:
I hope the guide help you to fix your problems.
Reference:
Boot-repair Homepage: https://sourceforge.net/p/boot-repair/home/Home/