I'm new to QGIS, so supect this is trivial, but it has frustrated me for the last hour or more... Last week whenever I added a csv as a layer once I'd filled in the first dialog it automatically opened a dialog where I could select the correct CRS. Today when I open a CSV file I go straight from the open CSV dialog to the map with a warning flagged at the top that the CRS was not set so it has used the default value, which is wrong. I must have somehow clicked some setting somewhere that has turned off the (very handy!) dialog and I can't find it anywhere. What have I done wrong and how can I get QGIS to automatically open the dialog again?