WeTransfer is currently unavailable in China due to government restrictions commonly known as the Great Firewall. This is outside our control and not something we can resolve on our end.
Workaround
A VPN may allow you to bypass the regional restriction and use WeTransfer as normal. This is the only workaround currently available.
If you're on a paid plan and are unable to use the service because of this restriction, contact our Support Team and we'll do our best to help.