How do I get the WhatsApp chat history after switching to iPhone?

Hi, so I switched from An android to an iPhone a few months ago and used a third party software to transfer all my messages which worked perfectly fine and I had all my older messages from a few years back. I noticed today that somehow I don’t have these messages anymore and they got deleted from the history.

I can’t see messages past the date I’ve set up my iPhone. The weird thing is if I use search I can’t see the messages but nothing inside the conversation itself older the October 2021. This is so frustrating if someone might’ve an idea what’s going on please help me. Thanks

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