20 Most Recent Smeg 28 in. P752 Electric Cooktop - Page 2 Questions & Answers

It may be dirty. Try cleaning it and let it dry.

It's stuck on the runner,only way is to use a wood pry tool to force it open

My guess is the heating element has gone. Get online and search your domestic appliance web sites quoting the make / model / serial number etc and see what element is needed. If you are capable of good DIY and know how to isolate the cooker then its not a big job to replace. I've googled your model and the elements are readily available. You don't say where you are but the elements are readily available in UK for between 20 and 30$. I had a similar problem with my double oven and found a suitable height table, covered in news paper, slid the oven out of the unit, changed the element, all done in under an hour. If yours is under worktop then slide onto a piece of board on blocks.

their can be a blockage in your pipes or gas low.