I know of at least two possible reasons:
1. Spotify have server hickups — either publicly visible ones, or simply temporary internal
Keep in mind this could affect your libspotify applications, but not your desktop or mobile
clients. If it works on one platform does not mean it works on another.
2. Your local cache has been corrupt. libspotify keeps a cache directory, and sometimes
this directory can collect garbage that confuses libspotify — this could be the effect of libspotify
crashing, or simply running long enough. libspotify is not the most stable piece of software.
Remove the cache directory to resolve this particular issue.
With this said, like I’ve mentioned earlier, libspotify does not guarantee that objects load in
a reasonable time. Sometimes things simply don’t load. Unfortunately it’s kind of common,
which is why Hallon have #load to begin with (otherwise I’d just have made it automatic —
today I’d rather just do some other approach entirely if I were to rewrite it!).