Hi Claudete,
It looks like there is no easy fusible link to replace, so something is probably burned out on the control board.
[guide|62805|Follow this guide] to take the mixer apart to the control board (step 6). See if you can see any burned components. If you reply with a picture of the board ([https://d3nevzfk7ii3be.cloudfront.net/igi/y2hNhDMwQwOlEsEB.huge|like this]), we may be able to help identify what part is burned out.
The cheapest solution may be to buy a replacement board, or go to an electronics repair shop.