Leisure range oven timer and fan oven stopped working

I have a problem with Emmy Leisure range oven which perhaps someone can help with. A couple of weeks ago the timer suddenly stopped working, went blank, and so the fan oven stopped working too as I u destined the timer controls this oven. The rest of the range is working, gas burners, electric grill and second electric oven all working fine.

After looking at your forum I bought. Replacement oven timer and thought I would have a go at fixing myself, being ridiculously independent! I wasn’t sure how so eventually called an engineer, after 2 no-shows I decided again to attempt myself and I have now fitted the new timer,,,,,hey presto the new timer does not work!

I am working on the assumption that the part is not faulty, purchased from UK white goods, but is there something I am missing, somebody mentioned a thermal cutout, could this be the problem?

I would obviously rather have left this the experts and I may have to call somebody again but would like to know the problem before I do or if I could fix myself?

Many thanks