If you replaced your old passport, I think you need to enter hong kong manually - ie fill out the paper work and see an immigration officer.

Once processed, you can make you way to the e-channel enrollment station and request a new barcode.

The new barcode will will be valid for the life of your new passport. If it's 10 years, you get 10 years*.

Note! If you arrive 'manually' and get a new barcode, you can leave via the e-channel booth on your exit from HK (ie, just because you were processed manually on entry doesn't mean you need to be processed manually on departure).

*'life of passport' I think means the life of the passport as accepted by HK for immigration purposes. I attempted to enter HK on a passport with just under 6 months left on it... the e-channel didn't like that and and officer had to come let me out and send me to an immigration booth.