if your keyboard settings are set properly, check that the keyboard is fully updated. sometime the keyboard or other default stuff don't update on time as they should.
You can also submit error report to Samsung Members after reproducing the issue, the engineers at samsung should be able to look into what is causing predictive text to not show.
Could you share the device model number, software version and the keyboard's app version? thanks
software version is found in Setting > About Phone > Software > Build Number (last 4 digit).
I'll just test on the latest sw version and let you know. BUH2 should be the latest version if i'm not mistaken...