Problem to synchronize android source code

I follow the radxa wiki page to download the android 8.1 source code, but when I sync the code after I have initialed the environment and downloaded the repo, it still has errors. More specifically, the errors are can not access the tsinghua mirror website. So is there anyone can give me some ideas?(I put the error below)

fatal: unable to access ‘’: gnutls_handshake() failed: The TLS connection was non-properly terminated.

It’s a network problem.

Yeah, I suspect it maybe the bad network connection, so I tried to open the on my chrome and it works.

I tried to use VPN but it still has the same error. And I downloaded the AOSP from the tsinghua mirror directly, also failed…

try this link:

I can access this link