Hi, I'm John! I will help you with this.
To help narrow down the issue:
- Were the old files stored in personal OneDrive or OneDrive for Business?
- When you open Office apps, which account appears in the top-right corner?
- Can you still sign in to the old Gmail-based Microsoft account?
In the meantime, if you haven’t already, please try this first:
- Open Word or Excel
- Go to File > Account
- Sign out of all accounts
- Restart the PC
- Sign in with the old Gmail Microsoft account first and check if the files appear
- After that, add the Business account separately if needed
Also check both OneDrive portals because personal and business files are stored separately.
Please also remove or blur the full email addresses from the public post for security reasons.