I would send it back.  I got a instruction manual from Nelson when I ordered Urac from them.  The shelf life is 12 months if I remember correctly.  I had some Urac that was 18 months old (before I read the shelf life), it didn't work out well.  Of course, I'm still perfecting my glue ups.  But, when I got my new batch of Urac from them, the resin, liquid was much lighter in color and a lot thinner than the old stuff I had used.