Car won't crank, fuel gauge does not work, locks do not work

These 3 things happen all at once never separately. Car ran fine all weekend and to work this am. After a 9 hour workday, car would not crank. The gas gauge would not register neither would the locks work. Last week, I purchased a new battery when the car would not car as the battery in the car was the original. Last year, the same things happened and a mechanic did so work on the grounding system and this worked for several months but now it's all happening again. Bought this car new, and other then never replacing the battery, I have done all the maintenance work.
Any suggestions on what's going on?