Why is my More Pet Slots Script Not Working in Game?

local plr = game:GetService("Players").LocalPlayer;
local id = 7920230
    local tr = 0
        while true do
            wait()
            if game:GetService("MarketplaceService"):UserOwnsGamePassAsync(plr.UserId, id) then
                script.Parent.Text = tostring(tr).."/8"
            else
                script.Parent.Text = tostring(tr).."/4"
            end 
            for i, v in pairs(plr:WaitForChild("PetsEquiped"):GetChildren()) do
            if #plr:WaitForChild("PetsEquiped"):GetChildren() >= 1 then
                tr=tr+1
            end
            if game:GetService("MarketplaceService"):UserOwnsGamePassAsync(plr.UserId, id) then
                script.Parent.Text = tostring(tr).."/8"
            else
                script.Parent.Text = tostring(tr).."/4"
            end  
        end
    tr = 0
end