Get up to speed, 5th gear or so, then brake and shift down through to 2nd: It won't engage 2nd. Bring to a stop, shift to another gear, and it should allow you to shift back to 2nd. I don't think I'm clutching incorrectly, I've tried it a lot and it doesn't happen with other gears and it happens consistently with 3rd-to-2nd. My shifter doesn't have problems in other sims.
My guess is that its because your 2nd is to low compared to the gear you shift down from. So some kind of realistic (or unrealistic ) gear lock prevent the 2nd to get engaged. I admit this shift down prevention also irritates me - but I have get accustomed to it from both iRacing and other video games.
You can test if its an gear shift prevention issue by setting your G2 very close to G3 and see if the shift dows still doesnt engage in G2. But you have probably tried that allready. Could be a AMS2 shift down issue
Edit- Disregard. Im an idiot. Formula trainer is 4 speed sequential! Duuh Not sure if its related but try putting the formula trainer in neutral while cruising in 2nd-4th (I have an H shifter with pedals, automatic clutch OFF obviously). Then pay attention to the rev counter on the display and see if its what you're expecting to see.. then try pushing on the throttle.. Seems I cant select neutral while the vehicle is at speed. Is this expected/normal behaviour for the formula trainer?