A new website was created for SYC over the summer of 2015 and went "live" in September 2015. The new website was based on a extract of the data on the old website from sometime in the early summer of 2015.
Therefore, if you registered on the old SYC website aster the "cut" of the data was taken from there, then your registration wouldn't have been carried across to the new SYC website.
You will need to re-register on the new SYC website - go here.
For more details about other changes that came in with the new SYC website, please see this article.