Tefal Oven faulty LCD DISPLAY

take it in to an appliance repair shop as it may be the elements or thermostat control that is faulty
get a quote as the repair may be more expensive than a replacement unit

something had been gone short due to the power socket.let the socket be ok but sometimes due to heavy voltage this could possibly happen.just check if somme parts is burnt ,turned black or smelling foul oudor,or when you on the machine now it passes burning fumes from some where.

Try here

https://searchmanuals.net/search7/?keyword=%2Bowners+%2Bmanuals&gclid=CjwKCAiAqt7jBRAcEiwAof2uKwzE1jBmBNKl9hqWd4TyeToXsj80tGOrdxRc3s6LGEWtoEA-xsOXLBoCIhQQAvD_BwE

If the oven is not working, the fan is not working, and the light is not working, it suggests that the oven switch is faulty as that is the only common part for all 3 things. It might be a broken wire or a faulty switch. You will need to dismantle the oven to gain access to the switch and then use a multimeter to test it. if you do not know how to do this, then get an electrician or oven repair company to help, as there are dangerous voltages inside an oven than can give you a shock or kill you.

it happens commonly with LCD we can do nothing replace the display unit

If may be the thermostat is gone bad
Buy a cheap one a throw it away after guarantee expire

http://kitchen.manualsonline.com/manuals/mfg/tfal/5252.html?p=3

What is the actual temp of the oven? Not what the display says? If the conveyor running normal? If so you just need a display board. Depending on what temp is there are many possibilties after that.

You can download the manual here:
http://safemanuals.com/user-guide-instructions-owner-manual/TEFAL/AVANTI-_E

Follow this link and it will have what you need. I hope this helps you.