So, did you not attend your ERM on Feb. 12? If so, then the conviction is correct since you failed to attend. I hope you didn't just rely on the 30 day time frame provision as some sort of perceived fatal error and not attend your ER--is that what you did? If so, I wouldn't say that because it will not be re-opened. If we were talking several months in delay, you might be able to appeal and raise the 'prejudicial effect' of such an error, but in your case, we are only talking a matter of a few weeks and they would send you home quickly.
The good news is that JP's are generally good about allowing a re-opening if you can establish that you didn't know about the ER date (or some other emergency prevented you from attending). In your case, you'll have to establish that you didn't read your emails before then and did not know about the Feb. 12 date, especially since you are the one who requested a re-scheduling. The court's view is that you should have been following up on when your new date was. That said, the chances are still good that they'll allow the re-opening if you simply word things correctly (without lying of course!).
Oh, and by the way, early resolution meetings are actually scheduled by the court office; not the prosecution's office. Its all done by court staff; not employees of the prosecutor's office since the notice is a court document.