Did you attempt to plug it in with polarity reversed or does the new lipo have a bad (low voltage cell) cell? Some escs spark when connected anyway (to charge the caps in the esc), so the spark could be normal, but if you reversed the connection, you could have damaged the esc and the lipo.

What does the lipo show for voltage? Did you check voltage before attempting to connect it? These are not delivered with a full charge when new, so the 1st thing you should have done was to charge it fully.