UR error code on Samsung washers could be due to number of reasons like addition of excessive laundry, issue with control board or driver belt. If the issue is minor, you can try fixing it yourself if you are comfortable with it. I recommend to follow this guide: https://www.easilyfixit.com/samsung-washer-ur-code-causes-and-solutions-to-fix/

However, if you are not experienced with troubleshooting appliances, I recommend to seek expert help or best is to contact Samsung support.