The manual doesn't tell us what all the different error numbers are sgadsby but it does tell us what to do about it.
In your case you turn the speed selector to 'open lid' position and then to closed lid
Sometimes just turning the machine off for a while then back on will fix the problem too. Sorry, that's the best information I can give you - a consultant may know exactly what error 31 means though.
Welcome to the forum with your first posting. How are you getting along with your machine, how long have you had it etc? Perhaps you could pop over to the Introduce Yourself section on the home page and tell us a little more about yourself.
