Update...

Well, I think I found a "workaround" for this problem...partially.
Once I completed my reservation there was an option to add ancillary services. I clicked on this and magically the "comfort seats" appeared on the seat map.

In my case being an AF SkyTeam Elite+ I shouldn't have to pay but the system asked me for 25€. In the past the calling center was able to help with this but they refused this time and said they had no authority to override this... (hmm).