My experience was different but still indicated a problem.

Astro::Montenbruck and Astro::Montenbruck::CoCo were always found. I tried reloading and bypassing the cache (Ctrl-Shift-R on Firefox) multiple times.

Astro::Montenbruck::Ephemeris always gave "404 Not Found". Again, multiple attempts to reload and bypassing the cache.

I had a look around a few places (Home, About, News) but found nothing mentioning a problem.

I'd give it some time to see if this gets fixed. If it doesn't, use one of the methods shown in Contact to report the issue.