Hi Andy,
We’re always trying our best to help you find the solution. Could you please provide the following information to help me address your query quickly?
1. Because “using an Office 365 credential to activate the Office for Mac” is a new functionality in Office 365 after-upgrade (released in 2013), I’d like to confirm where you downloaded the Office for Mac and how you activate the Office for Mac one year ago. Have you ever re-downloaded it from the Office 365 portal this year?
2. What's the full name of "P1" subscription? Typically, the P1 subscription stands for the Office 365 Professional and Small Business subscription that doesn’t include the Office Professional Plus license by default. Users need to purchase additional licenses if they want to use the Office suite. Could you capture the screenshot about “license details” of your current account? Here is an example of my Office 365 Small Business Premium subscription.
3. Does the “upgrade” from the beginning of your post mean the “Office 365 service upgrade”? If so, have the service upgrade for your organization been finished? If you are not sure which version of Office 365 you are using, you can check it from this article: Am I using Office 365 after the service upgrade?
4. I notice the Office applications work fine on your virtual PC. Does this virtual PC also install the Mac OS(operating system)?
Thanks,
Maggie Li