[SOLVED] How do I fix the 'Unable to cast int64 error'?

I'm trying to make a gamepass, and make it see if the player owns the gamepass, if not then a gamepass will get prompted.

Here is my script (it's a local script):

local gamepassID = 49956565
local MPS = game:GetService('MarketplaceService')

local plr = game.Players.LocalPlayer
local button = plr.PlayerGui.GamepassShopGUI.MainFrame.TwoTimesClicksFrame.BuyButton

button.Activated:Connect(function()
    if MPS:UserOwnsGamePassAsync(plr, gamepassID) then
        button.Text = 'You already own the gamepass'
    else
        MPS:PromptGamePassPurchase(plr, gamepassID)
    end
end)

The error is on line 8.

Thank you for reading.