Line not showing

[Ofnuts]

Several possible reasons:

1. the line is the same color as the layer
   
2. there is a selection somewhere (drawing is effective only in the selection (Select>None to remove)
   
3. you are trying to draw outside of an existing layer (btw what do you mean by "loaded new canvas"? No layer in the image?)
   
4. the pencil tool is not in "Normal" mode (mode selector at top of Tool options)
   
5. the layer mode is not in "Normal" mode (more selector at top of Layers list).