Users having Office software installed on their Windows PC as a part of some Office 365 for Business subscription may be required to switch to the different version, if the organization decides to switch to different Office 365 for Business plan. To make the transition simple and notify you at an opportune time, Microsoft displays the following message, after a certain grace period of 1-3 days.
Account Notice: Your Office 365 subscription has a pending change. To keep using your applications without interruption, please sign in now.
Disable Account Notice message in Office 365
If you find the message quite bothering, you can disable the message by either updating Office (if you have Office 2016), or reinstalling older version of the Office software (if you have Office 2013).
At this point, it is important to mention that you should have that version of Office installed which comes with your new plan. If you ignore, you will eventually see Unlicensed product errors.
Depending on the version of Office to be installed, you may find a handful of apps, such as Access missing from the bundle.
To update or reinstall Office, pick the version of Office you currently in use and then follow the steps. The procedure here is for Office 2016.
Click the Update button in the Account Notice dialog box. When prompted, sign in.
The Office tool will instantly start downloading updates for you and complete the conversion in the background. Upon the completion of the process, the old version of Office will be uninstalled.
If you chose not to install the version of Office that comes with your new Office 365 for business plan, Office software will flash the following message (Unlicensed Product) in the title bar:
UPDATE REQUIRED. Your Office 365 subscription has a pending change. Please apply the change now to keep using your applications and eventually, Office will enter reduced functionality mode with most options greyed out or functions disabled. Install the new version so as to see all features of Office working.
For more on this, you may visit Office.com.