Whatsapp search not working after getting new iphone

I backed-up and restored the data on my old iphone to my new iphone using itunes.

All the data is on the new iphone, however on Whatsapp, whenever i try searching through my old chats which are all present, all the results are only from when i started using the new phone, so i can't search any of the messages on chats i had previously.

I even tried using spotlight search, but no results show for whatsapp chats at all.

How can i fix this?