When I leave my 2007 Maibu two days or more without starting the battery goes dead.With a quick jump it starts.
Overnight it usually starts normally.
Have your local auto parts store check the battery and charging system. I suggest that first since it is generally free and it can rule out some possibilities.
Beyond that you need to have a meter capable of measuring current (not just voltage) and measure the drain with the engine off. Remember that the drain will usually go up and down a few times after you shut it off so just one reading is not enough.
The battery is new and they said it is charging correctly
There is a power drain on the battery, something is causing a load on the battery when it shouldn’t be. You need to have a shop check the system out for a parasitic current drain.