Looks like vacationPacakageDetails.fullDueDate is on the experience event schema ?
Accessing experience event attributes via #{ExperiencePlatform.ProfileFieldGroup.timeSeriesEvents._xxxx.vacationPacakageDetails.fullDueDate} will not work (if you are using this in a batch journey starting with a read audience). You will need to have a segment defined (with dueDate logic) which can be used in the journey
If you are using this in an event triggered journey, you will have to adapt the expression accordingly
toDateOnly(toString(<Experience_event_attribute_pointing_to_fullDueDate>))==toDateOnly(toString(nowWithDelta(14,"days")))
This is assuming fullDueDate is a not within a array or array of objects