OK, I'm looking at the 2.6 belt routing and just like on my 2.3, you want to put the belt in place, then do the water pump pulley last. As you can see in the belt diagram, when you pull up on the belt to put it on the last pulley, the tensioner will move to allow enough slack to get the belt on.
You stated that the tensioner is moving freely, so, check and re-check the belt routing, and try pulling up on the belt to put it on the water pump pulley last.
BTW, is this the same belt you removed before you replaced the fan clutch bearing bracket?