You did not tell us your model number, so I cannot be specific to your model.  It's possible that some crumbs or debris have gotten underneath the button. You could open the laptop to check and to clean. Depending upon the button design, you might be able to clean the contacts with some 99% alcohol. To regain normal function, you might need to replace the power button. On some models, it's a small separate component that you can buy and replace. On other models, you might need to replace the entire palmrest or keyboard. A reliable source of genuine Dell parts is Parts-People. You can search for your model to see what's available. You should also look at Dell Support site for your model's Service Manual or Owners Manual, to see what would be involved to access the power button. If you live in the US, Parts-People (specialists in supplying genuine Dell parts and repairing Dell computers) offers a laptop $100 Diagnosis and Repair service, whereby you pay just $100 + parts for repair, with free return shipping. If, after receiving their parts estimate, you decide against the repair, you pay just $30 for their diagnosis + return shipping cost. Whenever touching components or working inside a computer, wear a grounded wrist strap, also called anti-static wrist strap, ESD wrist strap, or ground bracelet. It's a cheap and sensible precaution. Rest the laptop on an anti-static mat or at least a reasonable alternative such as corrugated cardboard. (Repeatedly touching a metal case part is not sufficient mitigation with modern components.)
I have Dell Latitude and it's power button not working anymore. Sometimes it works when I pushed with force, otherwise not. Any solution?
Power Button not working