A recent model search in 3dwarehouse proved difficult re: 3DXchange as almost all model downloads on the site now are for sketchup 2017/2018.
Xchange only supports up to sketchup 2015.
Whilst I appreciate that there are still sketchup 2015 models available for download on www, 3dwarehouse is the prime source and linked to 3DXchange as standard.
Please consider upgrading support.