Office 2019 files converted to Office 365

The first recommendation from me to consider is removing Office 365 Shared Computer Activation. To do this, head to your 'Control Panel,' find 'Programs,' and select 'Uninstall a program.' Look for 'Microsoft Office 365 Shared Computer Activation,' and hit 'Uninstall.' Just follow the on-screen instructions, and you'll be good to go.

Now, onto the second suggestion. Let's tackle the Office 365 Sign-in Assistant. Navigate back to 'Control Panel,' go to 'Programs,' and select 'Uninstall a program.' Find 'Microsoft Office 365 Sign-in Assistant' and, you guessed it, click 'Uninstall.' Follow the on-screen prompts to wrap that up.

Moving on to the third point. We want to tidy up your Windows Credentials. Open up 'Credential Manager.' Under 'Windows Credentials,' choose 'Web Credentials.' If you see anything with 'Microsoft Office 365' or 'Office365,' click it and hit 'Remove.'

Finally, the fourth step is easy but crucial. Restart your computer. Once that's done, launch your Office 2019 apps. You should be all set without Office 365 prompts.