HI there! I know this is a dead thread, but I wanted to throw in my 2 cents since this is the thread which popped up when i searched for the issue.
I was having this exact issue- unable to download a file via the launcher, cant ping libraries.minecraft.net, but could ping minecraft.net.
Turns out the DNS server my computer was automagically getting assigned was borked. What fixed it was:
On December 8, 2016, it was announced on Mojang Studios' official blog that they would be moving all Minecraft related news to minecraft.net, and continue to update it there, rather than on mojang.com as they had done in the past.[2]
The home page of minecraft.net consists of the Minecraft franchise logo and a link to buy the Minecraft game. Below the banner is a list of current Minecraft games and add ons and below that is the blog section with Minecraft news, insiders, and featured creations by the community.
A. Any viewer with a Twitch account can participate in the campaign to receive a Minecraft item code. However, reward redemption codes can only be redeemed on minecraft.net/en-us/redeem from any country that Minecraft is currently available.
A. If you have successfully received your reward redemption code on Twitch and are having problems redeeming reward items in minecraft.net/en-us/redeem, please contact Minecraft support here for questions or support regarding redemption of reward redemption code.
The Minecraft assets server (assets.minecraft.net) hosts versions of Minecraft ranging from 1.8pre1 to 1.5.2. Due to the new launcher used within recent snapshots downloading everything from a different server, the assets server hasn't seen a new snapshot get uploaded to it since March 19, 2013. An archive can be downloaded below.
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