WARNING: This page is about a different car, the 2011 BMW 750xi, 2011 BMW 750Lxi, 2010 BMW 750xi, and 2010 BMW 750Lxi. However, it is still accessible from the selected car via links, so may be relevant.
Press in lock (1) before installing quick-release coupling.
Push on hose.
Quick-release couplings must clearly snap audibly into place.