We had a look at the file, and the kerning works just fine for us in Version 2.4.2 (991). Please make sure you are actually testing the right version. You are aware of these tutorials?
Are you using the Adobe fonts folder to test your font?
Testing Your Fonts in Adobe Apps: https://glyphsapp.com/tutorials/testing-your-fonts-in-adobe-apps
If it was (also) installed otherwise, it could also be a font conflict or font cache problem.
Eliminating Font Cache Problems: https://glyphsapp.com/tutorials/eliminating-font-cache-problems
To be absolutely sure, try exporting it with a different family name as decscibed in the Eliminating Font Cache Problems tutorial. If that fixes your problem, there is probably a conflict or cache problem.