The customer got the following error message on their Pardot integration event log: "IntegrationRequest failed and no fallback available."
I couldn't find anything related, it seems that she already disconnected and reconnected Pardot.
https://drift.lightning.force.com/lightning/r/Case/500PL00000Azuh5YAB/view
https://app.drift.com/conversations/3980816558
https://drift.slack.com/archives/C80EAM7R8/p1716923262055519
Both of these errors, {"error":{"message":"The access token is invalid or has expired", "type":"authentication_error"}} and IntegrationRequest failed and no fallback available, are transient errors that don't actually relate to any specific sync requests and solve themselves.
In each case, there is no loss of data that is supposed to sync to Pardot at the time of the error, no action is required to either correct these errors or prevent them from happening in the future.