Greg Henninger (Community Manager) has posted a notice that trading will be disabled until the split happens on the 17th Feb.

In preparation for the game split, all new Steam Market trades will be suspended starting today (2/12/2016) at 3PM Pacific. Trading will come back online after the game split on 2/17.

Source: Reddit r/H1Z1

As a result of this annoucement and no H1Z1 items can be traded currently we will be closing our trading portal here on Survivors Rest until after the split. This will also give us an opportunity to implement and test our changes in preperation for supporting both games and their items after the split.

We will be closing all current trade listings and preventing any new ones from tonight until after the split.