Can help my simple codes?

Hi guys. Newbie here. Just start learning python.
I have written a simple code as below. I would like to show a popup message, but failed to do so. It just popped up a blank message. Can you help me and tell me what is wrong?

Thx you in advance.

from kivy.app import App
from kivy.uix.button import Button
from kivy.uix.label import Label
from kivy.uix.floatlayout import FloatLayout
from kivy.uix.popup import Popup

class CustPop(Popup):
    def build(self):
        lb = Label(text="Welcome Here",size_hint=(1,0.8),pos_hint={'left':1,'top':1})
        bt = Button(text="Press Me", size_hint=(1,0.1),pos_hint={'left':1,'x':0})
        fl = FloatLayout()
        fl.add_widget(lb)
        fl.add_widget(bt)
        cp = Popup(title='Guys', content=fl)
        return cp

class t6App(App):
    def build(self):
        cp1 = CustPop()
        return cp1
        
t6App().run()

Thx.
It is fixed somehow.