Sorry to hear this Moon, first one motor seized, now the replacement with a charging problem, lightning striking twice. Unusual though, most of these bikes are very reliable.
However, as yours was a brand new replacement on 31st May, just get in touch with David Miall at Wisper straight away, he'll remember you from when he delivered the bike and I'm sure will solve your problem. Maybe trying another charger will reveal if it's that which is the problem.
.