What's this PublishAsync() error?

My error:
MessagingService: PublishAsync(): Cannot publish Dictionary, can only accept valid UTF-8 characters.

My code:

local Data = {
    SenderUserId = Player.UserId,
    RecipientUserId = RecipientUserId,
    MessageText = MessageText,
}
MsgService:PublishAsync("ChatMessage", Data)

I was using FilterStringAsync() to filter the MessageText wrong. @JarordOfOrbiter made me second guess the value of the variable.

What is the MessageText you arew trying to save?

It’s “[Opened Direct Message]”.