Reward expiration is managed by an expiration job that runs once a day. When this job runs, it expires all rewards with an expiration date of yesterday or earlier. This means that if a reward is shown to expire on 12/20/23, it will expire when the job runs on the day of 12/21/23. Most US-based customers will have their job run between 12am and 3am Eastern time, depending on the geographic location of their stores and their hours of operation.
Specifically when this job runs is dependent on a Paytronix admin side configuration called the Expiration Event Schedule. You can reach out to Paytronix support by emailing [email protected] to confirm when your job is set to run daily and request a change if needed.