The only source of this problem is your internet connection. People living in China and people who have connection problems like in China. If there is no VPN connection tab on your modem, first install VPN on your computer, then select Local area connection (network adapter) of VPN from Network settings. Go to the sharing tab and select Ethernet in internet sharing. Then connect your Raspberry Pi to the Ethernet port of your computer with an Ethernet cable. Then turn on the device. That’s all you need to do.
if you have any question dont be hasitate
Thank you.