Azure Advisor automatically refreshes recommendations every 24 hours by scanning and analyzing resources across all your subscriptions. Azure Advisor allows you to dismiss or postpone recommendations on a single resource. If you dismiss a recommendation, you do not see it again unless you manually activate it. However, postponing a recommendation allows you to specify a duration after which the recommendation is automatically activated again.
That being said, as you mentioned, you are not able to view the recommendations that were available last week even though you haven't taken any action. Whenever the automatic refresh happens, the non-relevant recommendations disappear based on the service usage telemetry.
For more information, refer this document.