They've been searching for dark matter/dark energy for a long time & have come up with zip. Recently the Large Hadron Collider
(LHC) explored the properties of nature at higher energies
than ever before, and has found something profound: nothing new. There are no particles below the level of Higgs so far, even though they were predicted.
It looks like we are going to need a new theory of the cosmos. Here's a radical rethought which will be rejected by almost everyone...but which actually works and explains everything: Expansion Theory. The basic idea is that EVERYTHING is expanding down to the subatomic level. The outward push would obviate the need for forces we can't detect. I know; I said it was controversial. Here's a review, first posted in Opednews in 2010, with high level math and everything!
Meanwhile, the search continues but it looks increasingly in vain.