What is the Singularity
Singularity is an automatic warning, which informs a user of a problem within the model, which prevents the analysis to be performed. Typically, there is a missing weld between two plates, etc. Singularity warning is displayed in the overall check immediately after start of the calculation.
You can go to the Check display and get detailed information of your model singularities in the tab in the Analysis section as well see the problem pointed out directly in the 3D window.