Add new FAQ pair about needing a new tenant for O365 account in M365

Author: Evan Windom

subscriptions/vs-m365.md

@@ -84,6 +84,9 @@ Not sure which subscription you're using?  Connect to [https://my.visualstudio.c
 ### Q: How do current users upgrade to E5?
 A: Currently, only new Office 365 Developer Program members will get the E5 offer automatically. Rest assured, we are working to enable all Office 365 Developer Program members to move from E3 to E5. Stay tuned for more information in the coming months.
 
+### Q: Can I activate Microsoft 365 using an existing tenant, or do I need to create a new one?
+A: To activate the Office Developer subscription, a new tenant is required.  
+
 ### Q: Can I choose E3 or E5?
 As of September 2019, new Developer Program members are only offered E5, which is our flagship version of Office 365.  This version of Office 365 offers even more value than E3, and can normally cost substantially more than our previous E3 subscription.
 
@@ -96,7 +99,6 @@ You can verify your version now in the subscription tile located on your Office
 
 Look for the E3 or E5 indication in your tile.
 
-
 ### Q: If Microsoft 365 doesn't include Windows, how do I get Windows?
 A: The Visual Studio subscriptions that include the Microsoft 365 benefit also include Windows as part of the subscriber downloads.  Visit [downloads](https://my.visualstudio.com/downloads) to download Windows. (If you don't see downloads enabled in your subscription, please [contact your administrator](contact-my-admin.md).)