At the beginning of the lockdown the government relaxed the rules about refunding season tickets. This meant that you could backdate your claim back to the last day you used the ticket and that the admin fee would be waived.
TfL are following these rules for refunds of travelcards stored on Oyster cards, but the process used for the refund initially follows the normal rules. This means that you’ll get back the refund due on the day of the claim, less the admin fee. As a separate process the applications are looked at again and a further refund of the days between last use and your claim, plus the admin fee, will be processed. At the moment this is taking around 2 weeks.
If you’ve been waiting longer than that then you can call the Oyster helpline. Call volumes have subsided significantly now the majority of queries have been answered so it is possible to get through.