It's pretty straight forward, anonymouse. You either missed something on the interview, or failed the SIMEX.
Assuming you did an S&P, you obviously met their "fit".
It's a shame the prospective employer can't give you any feedback. You can blame past litigious applicant's that didn't agree with the assessment
Because you don't know which aspect of the process you failed, I suggest you work on both components of the interview. 12 months is heaps of time to really sharpen your interview skills (and manipulative skills for the box).
Although I have not used them myself, I know of many candidates who used a Sydney company called Pinstripe Solutions and reported good success with subsequent interviews.
As for the SIMEX, you now have an idea what the flight profile is. That doesn't change much over time. Think about what you feel you could have done better. You're obviously an IFR pilot. Use every opportunity to practice an approach (commercial constraints notwithstanding). Got an autopilot? Switch it off and pole the plane around as often as practicable. Be quite critical of your performance and identify your weak areas. Get someone experienced in assessing IFR pilots to come along with you and take a look at how you fly IFR. Hire somebody if you don't know anyone!
Personally, I think those Flight Experience sims etc are of
very limited value, unless the "instructor" is a highly experienced IFR operator capable of giving you an objective assessment of your session. You would be better off directing your dollars to something more productive.
With regard to second time success: If you apply yourself between now and the next attempt, your chances are very good (in the order of 70-75%).
Good luck!