Veeam for O365 backup uses an Azure AD application to establish a connection to our Veeam for O365 backup portal. Therefore there needs to be a trust based on an Azure Application certificate. If this certificate is expired the backups will fail.
This article describes how you can renew the certificate in Azure AD.
Login to Azure AD and go to “App registrations”and look for an app called VBO 365 (if you have more then one VBO 365 app contact support and ask for the application id)
Click on the app and click on the certificate(s) behind “client credentials”
Now click on “upload certificate” to upload the new certificate (attached to this kb)
Download the certificate from this KB
Click “select file” to select the certificate
Now the certificate is succesfully uploaded
Now contact Copaco Cloud support to renew the certificate in our backend.