My 2009 chevy hhr ls won't shift into overdrive

Hello, performing professional diagnostic testing is necessary to find out what is going on with the inputs to your automatic transmission as well as the function of the internal components. No way to guess what's going on until you find out what data is going in and coming out of the transmission. Use this link to find some shops near you that can help with your concern: www.repairpal.com/repair-shops