No labels for buttons and textbox in authentication module

It does actually contain the label tags, but there's no text in them. Can you check your language file for the mod_jfbclogin.ini file (likely in the following location):
/language/fr_fr/fr_fr.mod_jfbclogin.ini

Once in there, check the values for USERNAME and PASSWORD, and set them if necessary.

Hope this helps, but if not, we'll help you figure out the issue!