If you are used to get suggestions while typing Viber messages and suddenly you stop getting them than it seems somewhat annoying. But don’t worry you can change these settings to get settings again.
Sometimes it happened while exploring the app you may accidentally toggle off the typing suggestion. From the keyboard settings, check the typing suggestion and switch it on.
Now you will able to get suggestions again. For chat extensions, you only get the suggestion if your phrase exactly matches the phrase prints in the chat extension. For example, if you write happy, it will immediately suggest you phrases like happy birthday, happy anniversary or such phrases.