我不能apt-get install或apt-get update
W: Failed to fetch http://sd.archive.ubuntu.com/ubuntu/dists/xenial/main/dep11/icons-64x64.tar Connection failed [IP: 91.189.88.152 80]
W: Some index files failed to download. They have been ignored, or old ones used instead.
我尝试了所有方法，但都不起作用。是因为我住在苏丹吗？我尝试了另一个镜像，但没有用。