Salesforce Exam CRT-550 Topic 9 Question 7 Discussion

Northern Trail Outfitters (NTO) is running a campaign for a brand new type of footwear inside Journey Builder. The entry event: Prevents contacts from entering the journey if "shoes" is not selected in their preferences.

Is based on a data extension which has Email Address as Primary Key.

A few weeks after launching the campaign, NTO's data analyst noticed a reduced email volume and that some contacts inside the data extension updated their preferences after the launch of the campaign. Even with the entry event being triggered every day, those contacts are not receiving the welcome emails.

What could be the reason?