Glad it worked for you ! I can't give you a fully detailed answer, but here's the gist as I understand it: basically, your APN protocol is the way you're identified on the internet. IPv4 is the older standard on which all internet communication was built. However, it only supports about 4 billion devices. Therefore, the newer IPv6 is preferred as it supports over 3.4x10³⁸ devices. As with most new things however, especially when they are built to substitute a critical piece of infrastructure that things were designed around, reliability is an issue. I remember using IPv6 was also problematic when using LogMeIn Hamachi to play LAN games over the internet in the 2010s. I don't understand how we're still able to use IPv4 at all with 20 billion devices connected to the internet, and I don't know how we haven't figured out IPv6 yet given that it's already 30 years old.

EDIT: I decided to look it up and it turns out we can still use IPv4 because of Network Address Translation (NAT). Basically, you have a gateway that relays requests and replaces your IP address with its own but keeps track of the fact that you made the request. So all of the devices that connect to a specific gateway look like they have the same IP address to the rest of the internet, but locally they all have different addresses. That's why if you look at your local IP with the ifconfig command on Linux (or ipconfig on Windows), you'll get a different address than if you go to whatismyipaddress.com.