We know that the dossier is a pack of lies. But we also know that Michael Cohen and Lanny Davis are congenital liars.
If the dossier is the key piece of evidence driving this whole investigation, and Cohen has never been to Prague, then the entire collusion trap and everything associated with it needs to be thrown out. This includes Manafort, Flynn, Poppawhatever and Cohen.
This also means that as a counter intelligence operation, it failed miserably.