You have to reach out to Zyxel support in order to download the latest firmware.
The appropriate firmware depends on the internet service provider and the network structure used, so it is not officially available for direct download.
I recommend reaching out to Zyxel support so they can find the right firmware for your situation.
Fill out the required fields in the support form
https://support.zyxel.eu/hc... and provide the following information:
- Who is your provider?
- Which technology do you use (XGSPON P2MP or SFP+ P2P)?
- Which firmware version is installed (full name)?
- Can a connection be established with this firmware?
I know it's a bit of a hassle. I went through this myself, but in the end they were able to send me the right firmware update.