InteriCAD T5 - problem with 2D going to 3D - ERROR 'less 3 vertex' - help please!

Question

Hi there,

Ive been working with InteriCAD T5 for years with no problems. I just created a 2D floor plan and wanted to send to 3D (update VR) and it had an error message saying 'less vertex 3' so wouldn't let me go into 3D. Could anyone help please? I cant work it out at all, it was fine last week.

THANK YOU so much,

Demi