Where can I get the update for GS1900-24HP?

I got the GS1900-24HP. In the web interface settings it says that revision A1, serial number starts at S15ХХХХХХХ. But on the product page, that is, here: https://www.zyxel.com/global/en/support/download?model=gs1900-24hpv2 there is nothing like that. This model is also not found in the search, only GS1900-24HPv2. But I would like to update the firmware. Where can I find the one I need?