Why can’t I update the Lost Mode message? An error displays “you can’t change the message for this lost item”

Hello embouck,

Thank you for reaching out to Apple Support Communities, and we'll be happy to help in any way we can. We understand you're having issues with updating a lost item message. To start, check out the informant here about how to add a message to a lost item: Mark an AirTag or other item as lost in Find My on iPhone

Please note: "You can add a message saying that the item is lost and include your phone number or email address." This should happen at the time you marked it as lost and there is no way to update the message after that. If that's something you'd like to see, please provide feedback for Apple about this feature here: Product Feedback

We hope this helps.

Cheers!