Thanks for your advice have a good dayHi Bici... welcome to the forum.
If you haven't already, download the Pendleton manual from Halfords website and follow their advice on battery usage/waking it up: The Pendleton battery has some operating quirks which have confused many users here before (you can search these; some may help).
You'd need a multimeter to check basic functioning of the battery/charger. But as the bike is only 6 months old your best bet is to take it into Halfords and ask them to check it for you.