You can be unlucky with batteries and a good company like Wisper will I am sure replace it.
If this is your first electric bike and you bought it around October last year there are some newbie mistakes that can effect lithium batteries.
You should not just throw the bike in a shed or garage when winter sets in and do nothing with it until you drag it out in the Spring.
The charge level in the battery could fall very low. Conversely it is not a good idea to leave it fully charged.
Somewhere about 60% is about right, and store it in the house, and check it from time to time.
None of this might apply, but looking after those expensive batteries is definitely a good idea.
I have carefully looked after the 400Wh battery on my 2015 Haibike Yamaha, and it is still working really well now in its eighth year and with 16,000 miles ridden. I am not the most diligent looker after of things, but a £650 replacement cost concentrates the mind!