if you have a dynamic IP address, it could appear that you are using a VPN. An IP address is the ID of your computer connected to the internet. Similar to your phone number. However, if the IP address is dynamic, the IP address will change. If you would be using a VPN, it would do a similar thing. A VPN hides your IP address with a different IP address if you are using the internet.
That's why it may show "VPN detected" even if you aren't using one.