@jake551: Can you try heading to Settings > General Management > Language & Input > On screen Keyboard > Manage Keyboards > All Off > Back > Select Samsung Keyboard > Smart Typing > Predictive Text. Are you able to activate the feature following these steps?
If not then, while you're still in the Keyboard settings, head to About Samsung Keyboard > Tap the 'i' in the top right > Storage > Clear Cache > Clear Data > Restart your S10. Please be aware that this will remove any personal settings from your keyboard. Let me know if this helps.