Help, our baby only sleeps in our arms!

Our 13 week old son is only content sleeping in our arms or in his SnuggleMe lounger. We have a Halo Bassinet and for a couple weeks he would sleep a good 3-4 hours in there, but now as soon as his back hits the bassinet he is awake crying. Looking for some tricks on how to successfully get him in his bassinet for the night. Any advice is appreciated and thank you!!