My issue appears when I work on polygons and I'm using WGS 1984.
With the autocomplete polygon, you have to start digitizing just inside an existing polygon, digitize the polygon you want to add to the existing one, then finish off by finishing inside an existing polygon
Thanks for answering, I did exactly like what you said but I still get that message, I get the message when I use WGS 1984 but when i don't use a projection it's just fine and I can digitize anywhere.
It sounds like your other data and/or your map are in a different coordinate system. You can only digitize in the coordinate system that the data you are trying to digitize in is the same, (if memory serves)