I recommend fully logging out of your personal Gmail account and then logging back into your FCS account.
To log out:
1) Open your Gmail and locate your profile picture in the top right hand corner of the screen
2) Click on the image to open a dropdown menu
3) Select "Manage Accounts"
4) This will open a new page and you should see your FCS and personal email addresses listed. At the bottom, click "Manage Accounts on this device"
5) This will open a new window and you will see your accounts again. Find your personal account, scroll to the right and click the 3 dots. Then select "Remove this account:
Your personal account will then be removed. Let me know if you have any questions.