Maybe Israel got green light from the Quartet to build more settlements? It's only sensible to NOT negotiate as long as settlements project is ongoing. Is freezing settlements an unreasonable "condition"? You could think it this way: Israelis do have also a condition for talks, they must be allowed to continue settlements.
Russia: U.S. plan to provide air cover for Syrian rebels undermines Damascus fight on ISIS (Reuters)
from the article: Israel accepts Quartet peace plan, urges Palestinians to follow suit