As the last entry stated, hearing back from them this early means something went wrong. In fact, several things did go wrong.
On the evening of the 17th, after the last contact, the night got very cold. Combined with human error, this lead to a two month supply of backup insulin being frozen, which makes insulin unusable. In preparing for this trip, Sebastien brought several times the amount of insulin he would need, just in case something like this happened. In the remote area he is in, he has to bring all the supplies and backups he might need during his entire expedition, since acquiring replacement insulin there is near impossible. Because of his careful preparation, he still has a sufficient supply of insulin, but he cannot afford any more mistakes.
The next day they made another attempt to reach Camp 1. The team was nearly hit by a bad rock fall along the way, but no one was hurt. The trek was very slow going, and their mountain guide/expedition leader became very sick. He was unable to make Camp 1, so they were forced to stay at 6000m, unsure if he could make it through the night. After only two hours, he developed pulmonary edema, which is very dangerous and can kill within hours.
Sebastien volunteered for the rescue to take him down to Base Camp in the middle of the night. They had to stop along the way, since the guide was unable to make it any farther. Sebastien left him on the trail with sleeping bags and finished the last hour of the trip in the dark. He walked along fields of rocks and ice, and said it was scary to think that if he got lost that not only would he be in serious trouble, so would the sick team-member. He did reach camp and got Sherpas and oxygen to help with the rescue. Once altitude sickness becomes this severe, coming back down is the only solution, so he will be going back to Tingri.
So tonight they will stay at ABC, and take another rest day to work out contingency plans; they have to re-assess what they can and cannot do. The summit window is now shrinking, and things have gone from bad to worse, to near catastrophe.