It is always best to include the full text of an error message, as this makes it much easier for people to help. You should also advise what sort of analysis you are attempting. This sort of error suggests no useful solution can be calculated. For example, there are no loads applied or every node in the model is fully constrained, or every node in the model has enforced displacement in all DoF. In each case, there is no effective solution to be run - although in the last case, one might like to get stresses, in which case, take the enforced displacement off just one of the nodes.