That's unusual, when you turn 70 you're supposed to reapply for your entitlement to drive. The ten year renewal just applies to the photocard, so you have to renew when you turn 70 regardless of whether the previous photocard is expired or not. I'd try to get through to DVLA, but I'm aware they're facing significant delays at the moment off the back of the lockdown. If you can apply for a renewal online then I'd do that because you can drive legally while it's being processed, even if the licence hasn't come back yet: www.gov.uk/renew-driving-licence-at-70