1970 Dart starting issues- key will not crank now

When everything goes South I go back and recheck everything that I had done recently.
Yes, verify that the bulk head connector is coupled together properly, maybe one or more of the male/female joints did not seat properly and got pushed back, look it over closely.
Check that the ignition switch connector did not get dislodged, recheck what was done on the turn signal repair,,
If you do not find the issue, it is time to get a FSM and a multi meter and check the circuits.
If you have not done that before do not be intimidated. Folks here will guide you. A cheap HF multimeter is all you need.