Go to WhatsApp Settings > Chat Settings > Chat Backup to ensure if there is an iCloud backup for your WhatsApp chat history

Delete and reinstall your WhatsApp from the App Store.

Verify your phone number, then follow the on-screen prompts to restore WhatsApp chat history

Jihosoft Mobile Recovery for iOS

Recover deleted/lost data from iPhone 6s+/6+/5s/5/4s/4/3Gs, iPad and iPod touch

Retrieve lost files by extracting iTunes backup if iOS devices get lost

Recover deleted/lost text messages, pictures, notes, contacts, call history, WhatsApp messages & attachment, etc

Selectively preview & recover the deleted/lost data you want just in three steps