OPTION 1: Restore WhatsApp Messages Locally
Step 1: The very first solution to your problem is to restore it locally by UNINSTALLING the WhatsApp Application on your device.
Step 2: REINSTALL it again.
Step 3: SIGN IN YOUR ACCOUNT in the newly installed application. Then, you will be prompted with a message that says, you are able to restore your backup after reinstalling the application on your device.
Step 4: All you need is to press RESTORE and your problem will be gone. But you need to keep in mind that the backup for your WhatsApp history is only valid for 7 days and after a week, it will be gone and you will not be able to locally solve the problem.
OPTION 2: Retrieving Deleted WhatsApp Messages by A Data Recovery Software
CONNECT YOUR MOBILE TO YOUR COMPUTER WITH A USB CABLE
ENABLE USB DEBUGGING THROUGH SETTING UP YOUR MOBILE PHONE
Choose the mode according to the operating system. Like this: android 2.3 or earlier, enter SETTINGS and click APPLICATIONS then click DEVELOPMENT and tick USB DEBUGGING
Next step that you should take is: SCAN AND ANALYZE THE DATA ON YOUR MOBILE.
Step 5: Lastly, you have to TAKE A LOOK AND RECOVER FILES FROM WHATSAPP HISTORY.
OPTION 3: Use FoneDog - Android Data Recovery
to Recover Deleted WhatsApp Messages
Step 1: Download and Install
Step 2: Select File Type
Step 3: Select Mode
Step 4: Select Files of WhatsApp Messages from Android to recover
Video Guide: How to Recover Deleted WhatsApp Messages From Android Phones
How to Recover Deleted WhatsApp Messages on Android
How to Restore Deleted WhatsApp Messages on iPhone