#36 Kerning class does not appear

[William NewOlder]

Hey there,
I am struggling with kerning by class after generating. The kerns do not appear... I fully followed this tutotrial and tried a lot of things, but nothing worked. I searched the internet also, but I couldn't find exactly my problem. Here are my actions

1. Validating font | Without problems.
2. Generating font
   
   

Font is TrueType so it's height is 1024. After generating I open the generated font with FontForge and no errors appear. All kerning classes are still where they where just converted in one class.
For Kerning I use only GPOS so it is not broken with GSUB

And if I see the preview of the font are write with it in an application, the kerning classes are somehow ignored.
This is how the preview looks

And this is how the preview should look like with kerning.

I hope there is a solution and that we will find it.