MacBook Pro won't switch on after battery replacement

Smc behavior is the correct one, a good starting point. Try unplugging the battery and then plug in the magsafe, Mac should be starting up on its own. If it does just contact iFixit and explain them what happens with the battery. If it doesn't something went wrong with replacement..some connector, some static on the logic board or the likes. This is just a forum where volunteers try to help each other, not the right place to ask for customer support. Here is where you need to go for after sales service https://help.ifixit.com/