Android 7 predictive text multiple languages
The same problem happened to me a few days ago, which was resolved thusly :


Go to the keyboard settings : Settings>Language and Input>Virtual Keyboard>Samsung Keyboard
Check that your languages are selected in 'Languages in types' 
Make sure that the "Predictive" option is activated.
Make sure that the "Auto replacement" option is activated.
Restart the app on which the keyboard was used so new settings are applied


That last point is the one that made it work again for me so I can type ugly things like "Holà yeah le clavier marche again" without having to slide the space bar.

This was suggested to me by the French Samsung support which answered (within a day !) the following :


  En effet, pour apporter une solution à votre demande, nous vous proposons d'effectuer les manipulations suivantes dans les "Paramètres" du clavier :
  
  
  ajouter le français et l'anglais dans "Langues et types" ;
  cocher le "Texte intuitif" ;
  cocher "Vérif. orthographe auto." ;
  Fermer et redémarrer l'application sur laquelle vous avez fait le reparamétrage du clavier.