Amslod ebike turns off and will not turn on

I recently bought a second-hand Amslod Hamilton MX-600. Yesterday it rained cats and dogs, but the bike kept functioning properly. Today I put in the battey and it turned on automatically. After fee minutes, it turned off automatically. I tried to power it on, but in vain. Only when I take the battery off and put it in again does it turn on. Soon it turns off again. I was told by the previous owner that it should be the keypad and that I should dry it with a hairdryer. I dit to no avail. Has anyone experienced anything semilar or has tips?