1. Accessed Control Panel > Selected the Microsoft Office Subscription > right clicked > change > Selected Online Repair
2. Removed all the stored credentials in the credentials manager (control panel > credentials manager) (I didn't need to do this - Brad)
3. Restarted the computer
4. Deleted the folder's below:
5. Sign in Word (opened blank document > file > account > signed out and signed in office 365 account)
6. Sign in to your Office 365 account (outlook.office365.com), click the Apps icon (9 squares on blue background) at the top left, and select OneDrive.
7. Click 'Sync', then click 'Sync now', and when asked to launch application select 'Microsoft OneDrive for Business' and 'Ok'.
Follow the prompts and you should be good to go.
Original fix posted here.