Hello @Stefano Azzalini ,
Welcome to Microsoft Q&A Platform. Thank you for reaching out & hope you are doing well.
I understand that you have a subdomain using an Azure Front Door managed SSL certificate and the certificate is expiring in 28 days without auto-rotating.
As per this documentation - For the Azure Front Door managed certificate option, the certificates are managed and auto-rotates within 90 days of expiry time by Azure Front Door. For the Azure Front Door Standard/Premium managed certificate option, the certificates are managed and auto-rotates within 45 days of expiry time by Azure Front Door.
If you're using an Azure Front Door managed certificate and see that the certificate expiry date is less than 60 days away for Classic SKU or 30 days for the Standard/Premium SKU, file a support ticket.
Hence, if you have a support plan, I request you file a support ticket, else please do let us know, we will try and help you get a one-time free technical support.
Kindly let us know if the above helps or you need further assistance on this issue.
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