It's possible that the Chinese firewall can cause problems, and that may vary. There are two ways to download a mod.
1) Click a mod in-game (on the mods screen). From China (and other Asian regions, and of course America) I think you are redirected to the USA downloads. You can disable the USA redirect with:
Options... Misc... Allow regional downloads: [no]
Maybe that can help.
2) If you were clicking a mod like on the website and it failed, we would need to know the exact message, maybe you can set LFS to English and report the message. This depends on LFS being installed with associations enabled, so that web links can be used to start LFS.
I think it would help to know if it worked for you before, and it has recently stopped working?