We are aware that some players cannot receive the “Wishful Invitation” ticket even after completing all listed requirements.

If you have already finished the quests shown in the mailbox:

• "The Dream Castle" (Merlin)
• "Friendship Is Everything" (Merlin)
• "Making Cents of Things" (Scrooge McDuck)
• "Scrooge McDuck's Grand Re-opening" (Scrooge McDuck)
• "Fishing Expedition" (Goofy)

…but still didn’t receive the “Wishful Invitation” ticket, please also check Remy’s progression.
You need to unlock Remy and complete his quest “A Restaurant Makeover” for the ticket to appear.