Zero downtime licensing was added in version 2021.1, so earlier versions of Desktop or Prep Builder do not include this feature. Additionally, zero downtime licensing only works for subscription-based licenses. Older "perpetual" Desktop Professional licenses (keys beginning with TD) are not refreshed via zero downtime licensing even if the version supports this feature. And finally, zero downtime licensing attempts to perform a silent refresh 14 days and 1 day before license expiration, and on those specific days only. If you did not launch Tableau Desktop or Tableau Prep Builder on the 14th day before expiration or on the day before expiration, no silent refresh attempt is made.
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