Samebike LO26 won't suddenly start

[Cervantes_]

Hi,

I'm from belgium, in the southern part of Belgium near the France and Lux border.

I've bought a samebike LO26-I 500W last year. I've made 512km with it without problems except flat tyres. ;-)
I had surgery in june and was not using the bike for around 4 months. I've charged the battery once during those four month but did not use the bike (due to knee surgery)
Battery was stored in my house at room temp during those four month.

When I put back the battery in the bike it was not starting when pressing the M. Nothing?
I took it back and charge it for maybe 2 mins till light is green on the charger.After charging I put it back and then press M and the bikes start. Everything looks fine for some minutes then suddenly the LCD turn off and I can't start the bike again.

Now the bike is not starting at all even if charger light is green. I measured voltage on the battery with a multimeter and it gave me 44.3v. This bike battery is 48v. Everythings looks fine on the bike.

I'm looking for help because there is no bikes shop that want to work on this bike.
What could be the problem?

Is it a battery problem or a controller problem or else?

Thanks in advance for your help.

Regards,

Vince.