React project cannot work on mobile platform

Basically it is a e-commerce website developed using React.js and we already make it run on PC. But it gets error whenever we check it using our mobile phone after we run build it and deploy it on the web server (in our case is in IIS web server). Our goal is to solve this issue(i.e. make our website working on smart device) and get back to normal dev routine. Feel free to contact if you feel like you can handle that.