Old oven does not turn on

Dear Ikea fans, I am new to the forums. I apologize for my German, but I try my best :). So I bought a used Ikea Dåtid oven. The person had not used the oven at all and it was unused for quite a long time. I have used it without any problem for the last two months. A friend of mine came by and played around with it. Since then it no longer turns on. I have tried everything possible, including what was in the manual, unfortunately without success. Does anyone have experience with the oven? Can someone help me? I am very grateful for any help.

Thank you very much and best regards Hissam

In the clock, you have a window on the right for the cooking time, there you can set the minutes, or a bell appears when the timer has run out. You have to keep turning the small adjustment knobs on the right, I don't remember if the upper or lower one, until you see the "Hand" symbol, then it works.