Auto start not working is certainly incentive enough to repair the actual failure!
You’ll need to have a comprehensive scan test to determine what is causing catalytic converter inefficiency .. Only then can a repair solution can be achieved.
Good luck 🍀
RepairPal Certified shops can diagnose and repair your 2015 Chevrolet Impala. They provide transparent pricing with a minimum 12-month or 12,000-mile warranty on repairs and services.