Guix Halts After "updating substitutes from …"

[Wamm K. D.]

Hey, hey; 'not sure what caused this but my ~guix~ command suddenly
started getting stuck, when I do a pull or try to install a package,
after

> substitute: updating substitutes from 'https://ci.guix.gnu.org'... 100.0%

I haven't let it run for longer than an hour but it just sits there and
doesn't progress any further. When I run ~guix upgrade~, it halts,
similarly, after listing which programs it's going to upgrade.

Anyone, possibly, know what this is (or, at least, how I might get
around it)?

Thanks for any help!