Chinese ISPs detect and throttle VPN protocols (especially OpenVPN and WireGuard) during peak hours. Astrill's StealthVPN and LetsVPN's proprietary protocols survive longest.
Switch to a different server/location (Hong Kong, Japan, US West usually fastest from China). Change protocol to "Stealth" or "Obfuscated" mode in your VPN app. If your VPN is dead for 24+ hours, use a backup — most travelers carry 2 paid VPN subscriptions.

