you can play with plungers and snakes and drano, but let the sewer guys
know what you've done.
since it's a new home, why not have the sewer cleaning company snake
out all mains including any outdoor downspouts and your basement
problem. listen to his report on your main sewer line. an experienced
plumber can give you the confidence you need to call him back in the
future when he shows up on the scheduled day and gives you a report of
the results. be home with your directions and questions.