A big typhoon hits Japan and a landslide happened in Kiso on July 9th.
Now only train services between Nojiri and Sakashita stations including Nagiso, gateway to the popular post town of Tsumago, have been canceled and busses are substituted. Express train “Shinano” services have also been canceled. Instead, you can take highway buses from Nagoya Bus Terminal to Matsumoto, but some of them are fully occupied. Another option is taking a train to Takayama then ride a bus to Matsumoto via Hirayu Onsen, gateway to Kamikochi (a free pass might be convenient). JR says the restoration work will be finished around Aug 9th.
Refer to this article for more details.