Why isn’t cargurus contacting seller and buyer to complete a sale?

Trying to buy this car I found and me and the
seller have both accepted to buy and sell the
car to me but we need cargurus to continue
the process but they haven’t got back to us
and it’s been 2 days, I called them and they
said that they would get back to me but need
did so I’m wondering if they really gonna get
back to us or I should give the seller cash. At
this point I see why I should wait for them get
back to me and I really need the car asap.