I have 20 polygons and when I tried to label the layer with the ID numbers only 19 appeared. For some reason my first polygons ID number is not being shown and I dont know why. Am I missing something vitally important? Any help would be brilliant, thanks!!
Does it work if you label with another data field?
Sometimes Labels are supressed, if there is not enough place for labelling.
I have found that polygons that do not have valid geometry do not label.
The green cross means that you either have 2 nodes in the same place or possibly you have a self intersection. This could be the reason your layer is not labeling.
To test this, run the Check Geometry Validity tool in the Vector > Geometry Tool menu. You should fix any errors that are found.
Once you have fixed this, your layer should label.
If the geometry is fine and the polygon is still not labeling it could be that the label is not shown as its overlapping with other labels. To test this, on the labeling dialog, choose the advanced tab, then click the Engine Settings button. Tick the Show all Labels (i.e. including colliding labels) tickbox.
This will make sure all labels display even if they overlap.