Cirrus uses a security certificate (also known as an SSL certificate) to encrypt all data as it moves between your M365 environment and the Cirrus application. To ensure the ongoing secure encryption of your data between your M365 environment and Cirrus you may need re-authenticate your connection as you did when you first signed up.

If your SSL Certificate has expired then your backup jobs will start failing with the error message:


AADSTS700027: Client assertion contains an invalid signature. [Reason - The key used is expired., Thumbprint of key used by client: 'ID', ... ]

We have a functionality so that you can use your own security certificate or have us generate one for you automatically.

To have Cirrus generate a new SSL Certificate, please follow the steps below:

1) Log in to Cirrus with an Admin Account.

2) Click the Settings tab in the bottom left of the window.

3) Click System.

4) Click the blue Generate a new certificate button.

5) Copy the code that Cirrus provides on the next screen.

6) Open then paste the code and follow the steps given.

7) Once the Microsoft steps have been followed, click Generate in Cirrus.

Help & Support

If you require assistance, you can access online help at or reach out to our Support Team via email at