If you have Office 2016 installed and activated, then install an Office 2019 app, such as Visio, you may run into problems:

• When you activate the Office 2019 app, it may break the activation of Office 2016
• If you re-activate Office 2016, it may break the activation of the Office 2019 app
• When you try to run an Office 2016 app, it actually runs the 2019 version

Download the fix-it tool from this website:

https://support.office.com/en-us/article/Uninstall-Office-from-a-PC-9dd49b83-264a-477a-8fcc-2fdf5dbf61d8

Basically, it uninstalls all MS Office apps and digs it out of the filesystem (and registry?).

Then go to https://account.microsoft.com/services if you need to download any software or find license keys.

1. Run the Fix-It tool
2. Download, Install and Activate Office 2016 Home and Business first
3. After that, download, install and activate Visio 2019