Tank problem?

Hi there,
I am using an aspire Mini Nautilus with an aspire CF VV+, I've never had a single problem with them until today. The battery is charged, I turn it on and there is blue light when I press on it, I can turn it off again without any problem and it's been charging for 4 hours now. The problem comes when I screw in the tank; as soon as I screw it in and press the button, the light blinks 4 times and that's it, nothing happens, I can't smoke. The first time I thought it could probably because I had not charged it properly, but after 4 hours charging it is still not working. Charger, tank and battery are genuine, I have already checked it.

Could you please give me any solution?
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