If the servers go down, these cars won't be able to charge with DC chargers at all (which requires the TLS protocol), and maybe not with home chargers either (which sometimes uses the TLS protocol).
That's also not a hard technical limit in the TLS spec, you can easily generate a self signed cert that expires in the year 3000 if you want, but it's voluntarily abided by from all the Certificate Authorities that want to have their root certs included in almost every web browser. It's _possible_ that EV chargers don't use common Certificate Authorities, but it feels unlikely to me.
I understand the need for an encrypted connection, but it is worrying to see cars getting built more or less like phone or web apps, and encountering the same obtuse issues.