Thanks Jamis, that's good to know, and I appreciate your suggestion re the fuse.
Turns out it is the Charger Receptacle which has failed. The power wire to the blue connector is open (the live side of the blue connector reads 52.4volts). I guess there must be some electronics hidden beneath the layer where the wires attach to the back of the receptacle. Not much chance of getting under there to fix anything.
I ended up contacting Ryobi and they have ordered a receptacle for me, but it is on back-order so who knows how long I will be waiting.