No don't think its that. I have just paid a payment (Friday) and my quote states valid if returned between 27/10/2020 and 26/11/2020 and that your last rental due has been paid which it has. Next payment is due 30 November, which if paid would then leave 4 payments. So my current payment takes me up to the 26th November. I did intend to arrange return in the next 2 weeks but lockdown might make that an issue
It's not mileage either. i'm well under and they don't actually know my mileage yet. I did 3yr/36000 and currently have 26628 on the clock - at this time in the rental I calculated it would be just over 30k
As I say, I'll have to phone and check but can't see what it could be.
It was all arranged through Volvo and is Santander finance. They've been pretty good/prompt in helping out (had a quote earlier in the year which I did have the same question on but never took it further).