This is one of the limitations of the holo project that shinobu is based on. There are sometimes shows that it doesn't pick up when it is airing for one reason or another. Then, later down the line, it can randomly pick up a show or episode that it hadn't detected before.

The technical reasons for this come down to the difficulties of parsing raw html or text strings of torrent titles. Often times, the titles aren't formatted in just the way holo expects, so it won't detect the episodes that release. This issue was one of the main motivating factors in creating a whole new bot that doesn't rely on this method for the creation of discussion threads. Coming to !anime@ani.social with the new season.