feng@tumashu:~ $ guix pull
fetching path `/gnu/store/1drx7dy1zakc0xs60nb0im1jbvxp11dj-isrgrootx1.pem'...
Downloading https://mirror.hydra.gnu.org/guix/nar/gzip/1drx7dy1zakc0xs60nb0im1jbvxp11dj-isrgrootx1.pem (2KiB installed)...
guix substitute: error: download from 'https://mirror.hydra.gnu.org/guix/nar/gzip/1drx7dy1zakc0xs60nb0im1jbvxp11dj-isrgrootx1.pem' failed: 404, "Not Found"
fetching path `/gnu/store/1drx7dy1zakc0xs60nb0im1jbvxp11dj-isrgrootx1.pem' failed with exit code 1
fetching path `/gnu/store/bcq7sqhg18b7b1q87j8z60d5hybsdafm-letsencryptauthorityx3.pem'...
killing process 3656
guix pull: error: build failed: some substitutes for the outputs of derivation `/gnu/store/hm8c3lfvxkspqg9g3hcb877lkiqriad9-isrgrootx1.pem.drv' failed (usually happens due to networking issues); try `--fallback' to build derivation from source
feng@tumashu:~ $