Have you tried raising the center post? Lift it gently around the edges with a toothpick or a bent paper clip. Avoid touching the button while you do this.
I will bet you a cup of coffee that the 450ma charger has a longer center contact, compared to the thread depth, than the 420ma charger.
As you attached the battery, the longer center contact pushed down the center pole of your battery connector.
For this reason, your 420ma charger might not make contact correctly either. If it doesn't, that verifies that the center pole of your battery has been depressed too far.
Pull it back up, stick a carto in and see if it works.
Honestly, on an 1100mah battery, a 420ma vs a 450ma charger isn't going to hurt the battery unless the polarity is wrong.
I would seriously doubt you hurt the battery by using 450ma.
You are supposed to use a kGo charger because it fits the connector and doesn't supply too many amps, which will hurt or destroy your battery. There's nothing magical inside a kGo charger that works only with a kGo battery, or vice versa.
You really do need a meter though, to quickly diagnose these kinds of problems.