You must connect your Microsoft 365 directory to Signitic. See the guide
For Windows x86 and x64 desktops, and tablets such as Surface Pro you must have an Outlook Office 365 version:
The 32- or 64-bit version of Office 2013 or later, running on Windows 7 or later
Outlook 2013 or a later version of the Office client.
Outlook Desktop, the current channel or the monthly channel are required to use the Signitic add-in with the versions:
Current channel: v16.0.14026.20000 (or later)
Monthly channel: v16.0.14131.20000 (or later)
How to know the version/channel of your Outlook desktop?
In Outlook, select File.
Select Office Account.
You will find your account channel below About Outlook.
To find out the version of your Outlook, click on About Outlook
Support via the new UI of Outlook on Mac is available in version 16.38.506.