Possible Clues:

• Acronymic anxiety about being excluded from the fun
• Anxiety about exclusion, for short
• Acronymic distress about being excluded from the fun
• Anxiety spelled out by the starred answers' starts
• Feeling that everyone's having fun without you, in modern lingo
• Nonparticipation worry, in texts
• Millennial's exclusion anxiety
• Angst about not having fun, in modern lingo
• Feeling that might be post-produced?
• Anxiety about exclusion, per a modern acronym