Debian preseed.cfg - Language not set

Solution 1:

Setting localization values will only work if you are using initrd preseeding. With all other methods the preseed file will only be loaded after these questions have been asked.

To get this working there are two options:

1. Setting localization as kernel parameters
2. Building a custom netinstall iso with a preseeding.cfg

Solution 2:

If you use build-simple-cdd then the parameters to skip language and keyboard questions are:

build-simple-cdd --keyboard us --locale en_US.UTF-8

The reason for that is that the pressed is loaded after setting these, just like @denny-crane said.