The internal IP address used to connect to your node may change. This is because the internal IP is an address that is assigned to your node by your router, rather than a set IP address that comes with you node.
This means that in the event you change your network (i.e., use a different router), it's expected that your IP address would change.
An IP address can also change in the event of a router reset, sometimes caused by unexpected power interruptions.
Sometimes external ISP providers will regularly change your external IP address. If this is happening to you, you'll need to go in and manually change the external IP address in the node settings every time it does.
Another solution is to talk to your ISP about getting a static IP address.
If your IP address has changed, you can always find your current IP using an IP scanner. For more information, check out: