Replaced ignition switch....replaced battery...no power??? What could be the problem???? Please help

Fuse failure likely the result of ‘reversed battery polarity’ at some point during battery installation. https://www.autogenius.info/honda-odyssey-2006-2007-fuse-box-diagram/ Also - TEST all high amperage fuses (maxi fuses) .. You’ll need to contact local locksmith for key programming - obviously the vehicle can’t be driven until that occurs - - even IF battery power IS restored.. However I really can’t understand why the key would need to be programmed unless another IGNITION LOCK CYLINDER was installed that required a NEW key (?).. Replacement of the IGNITION *SWITCH* has nothing to do with the IGNITION KEY ! IF you are having trouble with - OR - are just not familiar with basic automobile testing and repair - recommend seeking *hands-on* assistance from qualified personnel. Good luck!