Why am I getting "Not Authenticated" when I start MailMerge365?
If you start MailMerge365 and receive an error stating "Not Authenticated" this happens mostly with browsers or browser plugin that have strict cookie settings. This affects most Office plugins and add-ins and can only be fixed by turning off these plugins for the Microsoft 365 (aka Office365) website (or using Office on the desktop).
In the Brave browser, go to Outlook in Microsoft 365 (aka Office365) and then you can go to the Lion icon on your toolbar and at the top slide the "Shields" indicator the left (therefore disabling it for the Microsoft 365 website). This will allow MailMerge365 and other Office add-ins to work.