I had similar issues with kucoin. I was told by kucoin support that the API provides only the last 6 months worth of transactions. Their csv download option from their website also provides only the last 6 months worth of data. So you need to remember to download your transactions in csv regularly.
The good thing is that kucoin support generated the full history of my account in csv and emailed the file to me 2 weeks after I opened the ticket.