I believe what they are trying to tell you is to login from an IP address that is not masked by Cloudflare, not that you have to use the exact same IP that you made a withdrawal from. If you are using something like Private Relay on Safari, or Microsoft Edge’s built in VPN, it will give you an IP address from Cloudflare.
If there is something on your device or browser that might be changing your IP address, you can try disabling it to see if it solves your problem, otherwise, it might be something in Nitrobetting’s Cloudflare configuration that is causing your IP to be converted into a Cloudflare IP.
This is exactly what I have in mind when I read through the opening post and the screenshots of chat between OP and their live support. OP, by requiring you to login through original IP, I am sure to a great degree that it was their polite way to ask you to disable VPN and access them with your real IP.
I've been contemplating on the possibility of dynamic IP situation while reading through your second screenshot album when you confirmed on later paragraph. If you never use VPN, and those IP changing is purely due to dynamic system that your ISP adopt, I'll strongly suggest you to try to sort this miscommunication with their live support, see if we can get this resolved by making both parties be on the same page.
I can see that their representative was online relatively short time ago. Though I never have any communication with them, let me try to reach and greet them, see if I can invite them here and get this situation cleared.