The new vehicle payment cut off date of 31st December 2023 only applies to ‘new to scheme’ customers.
If you were already a customer on 1st Jan 2022 you will get it whenever you change to your next vehicle on the scheme (unless you have already received it as it is only paid once).
https://www.motability.co.uk/get-support/end-of-lease/cars-wavs/next-vehicle/new-vehicle-payment/
There is a ‘checker’ on the Motability website to confirm if/when you will receive the payment: