Static IP for Server
Your router gives the box its address on your home network. That address can change after the router restarts, and then everything that points to the old one stops working. A reservation makes the router keep the same address for the box.
You need: the admin login of your router. It takes about 5 minutes.
In short
This is the address of the box inside your home network, like 192.168.1.10. It is not your public IP.
The panel, your proxies and the rules on your router all use this address. If it moves, they break.
Find the box in your router. Reserve its address. The router does the rest.
Reserve the address
Step 1 of 2
Open your router's admin page in a browser. The address and login are often on a label under the router. Common addresses are 192.168.1.1 and 192.168.0.1.
Open the list of connected devices. It is often called DHCP client list. Find the line with the address you use for your box panel 1. Copy its MAC address 2.
What next?
This address works inside your home only. To reach the box from the internet, open your router for it, or use a VPS.