@Mohsen Rahimimoghaddam we are sorry to hear you're facing this issue. Did you make any changes to the CNAME records for your custom domains ?
If you have CAA records set up, make sure they allow DigiCert to issue certificates for your domain. You can add a CAA record like mydomain.com CAA 0 issue "digicert.com"
. Also, check the validity of the SSL certificate by opening the WebApp in a browser and clicking on the padlock icon in the address bar. This will show you the details of the SSL certificate, including the expiration date.