Why is my textbox.FocusLost not working? [Answered by me]

why are you handling guis on the server, you shouldn't handle guis on the server, also there is no need for playerAdded event, just get a question using a remote function from the client to the server, for example

-- Server
local questions = {{questionText = "What is 1 + 1", answer = 2}, {questionText = "Never gonna?", answer = "give you up"}} -- I don't use instagram so I don't know what the story question system is

local function createQuestion(text, answer)
    local newQuestion = {}
    newQuestion.questionText = text or ""
    newQuestion.answer = answer
    local index = questions[#questions+1]
    questions[index] = newQuestion
    return index
end

local function getQuestion(index)
    return questions[index]
end

local function getRandomQuestion()
    local rand = Random.new(os.time())
    local question = questions[rand:NextInteger(1, #questions)]
    return question 
end

game.ReplicatedStorage.GetQuestion.OnServerInvoke = function(player)
    local question = getRandomQuestion() -- Ask a random question or whatever, you can even send the same question e.g return questions[1]
    return question
end)

-- Client
-- Instead of firing askquestion event
local question = game.ReplicatedStorage.GetQuestion:InvokeServer()

if (question) then
    local questionGui = player.PlayerGui:WaitForChild("ScreenGui") -- "player" should be "game.Players.LocalPlayer"
    local qnaAnswer = questionGui:WaitForChild("QNAANSWER")

        qnaAnswer.Visible = true
        qnaAnswer.Frame.TextLabel.Text = question.questionText
        print(qnaAnswer.Frame.TextLabel.Text)
        print(qnaAnswer.Frame.TextBox.Text)
        print(plr.Name)

    qnaAnswer.Frame.TextBox.FocusLost:Connect(function(hasPressedEnter)
            -- Check whatever
        end)
        plr.PlayerGui.ScreenGui.QNAANSWER.Frame.TextBox.FocusLost:Connect(function(pressedEnter)
             -- code here
        end)
end

Fixed this by making another remote event and used :FireClient()