Where did I go wrong?

[sherrardk]

At to time, I cooked some frozen chips (skinny, French fries) in the combination oven thing. I followed the instructions to the letter but they took loads longer to cook than they should have done. I used the convection oven setting - should I have used the combination setting (where the grill and oven is on). Is there a rule of thumb as to which foods need to be cooked either by convection combination? Thanks.

[chris1957au]

My guess would be you simply overloaded the tray