It's not clear which oven mode does not work. There are several.
Fan oven?
Top element only?
Bottom element only?
Both top and bottom?
I wonder if the top element has failed.
The only way to find out for sure is to check the individual elements electrically.
It is also possible the mode selector switch has failed.
Are you confident to work SAFELY on electrics?
Can you cope if it throws a curveball at you?
Rjrh, January 2023