My Kalkhoff Impulse 2 bike won't turn on.

[Cabster]

Hello, I cycled to work recently with my 2016 pedelec without any problems, however when I was due to start the return journey the display refused to turn on and I had to cycle home without power and I really found out just how heavy the bike was!! I later noted that the current battery appeared to have been drained all of its power( but wouldn't recharge ) so I replaced it with a fully charged new one but the bike still refuses to turn on. Any ideas?