WhatsApp data can be backed up using WhatsApp’s own Chat Backup feature in iCloud Drive, which is separate from the iPhone’s iCloud device backup.
If you have neither a WhatsApp Chat Backup nor a usable iCloud device backup containing your WhatsApp data, and you have already reinstalled WhatsApp without restoring from a backup, there is no retrospective way to create a backup of chats that have already been lost.
WhatsApp cannot recover previously deleted or lost chats simply by creating a new backup after reinstalling the app. A new backup will generally contain only the chat data currently available in WhatsApp.
Before concluding that the data is permanently lost, check whether an older WhatsApp Chat Backup or a suitable iPhone backup is available. If a backup exists, you may be able to restore your chats from it.
Please contact the app developer via the --> App Support or WhatsApp FAQ , Or Restoring your chat history - WhatsApp FAQ or Contact WhatsApp