Can not install the language pack

I am trying to add the en-us language pack to my firefox
https://addons.mozilla.org/en-US/firefox/addon/english-us-language-pack/

But i just get the error info ,can not download this component cause the connection failed.
I am pretty sure my proxy is working, what’s the problem?
By the way,I have updated the firefox to the latest version 56.02(64 bit)

I just tried, and it worked fine for me.

Can you try again? Also, have the network panel of the devtools open, and see which connections are actually failing? I see at least one redirect, so it’d be helpful to check where you end up.

@Pike
I tried it today, An unexpected error occurred with red color showed .
still the same error info ,can not download this component cause the connection failed.

I have no idea to solve this,did you have log record for me to check?

Sorry, no good idea myself.