Does the nikon d3100 have an autofocus problem?

I just bought a brand new D3100 and it was working fine until the next morning. It wouldn't focus on any subjects.

I also have a Nikon D 3100, No issues till date.
Check the Battery Charge and clean the contacts… And start again.
All the best.

Most common cause is accidently moving the M/A switch on the lens to M

Check that the manual/auto focus switch on the lens is in the auto position (A or A/M position). See page 62 in your manual.

Nikon's kit lenses seem to have funky electrical contacts. Gently rotate the lens back and forth a few times, just like you're trying to take the lens off, but without pressing the lens release button. This is usually enough to clean the lens electrical contacts.

There's also a menu setting to place the camera in manual focus, but this is rarely the problem as it's hard to get to. See page 62 in your manual.