I decided to "answer" rather than comment.
In a nutshell most vocalists would say "Don't do it". If you're able to "sing" in normal voice w/o trouble I would think you just lost the feeling internally that tells you your technique is on. I'd go back to some old exercises and see if you can reconnect with the feeling.
In classical voice training we do things like lip trill to activate the resonance in the sinuses. We also do exercises to control breath, the rate of flow and pressure inside the body. Getting to correct feeling is an important part of knowing your technique is correct. Sometimes is sound right but feels bad, other times the opposite.
An example is passing from one register to another. I seem to be able to sing will in my upper and lower registers but the one note that defines the transition is problematic. This causes tightening up of the muscles in the neck, etc. The fix is not over practicing the note, but doing relaxation exercises to take your mind off your body. Things like rubbing the back of the neck, or tilting the head down, etc.
This example is a beginner's problem but it is meant to illustrate a point. When things aren't working correctly taking your mind off the technique can free you up.
Assuming that you are not suffering from other issues like dehydration, I'd go back to basic exercises and see if you can recapture that feel you have when false chords "catch" properly. Are you (or have you) taking vocal lessons, or using some sort of method? Or are you self taught?