AirPort Extreme connectivity

No problem. Here are the steps to perform a "factory default" reset on your Extreme base station:

• Start with the base station disconnected from power.
• While holding in the reset button, re-apply power to the base station.
• Keep holding in the reset button until the status LED starts flashing rapidly, and then, let go of the button.

Ref: How to reset your AirPort base station - Apple Support

Connecting the AirPort Extreme to a new or replacement modem requires the following simple steps:

1. Start with all devices powered-off.
2. Power-up, and then, reset the AirPort Extreme to its "factory default" settings. Then power-off the Extreme.
3. Power-up the modem. Let it go through its initialization phase. This should take 5-15 mins. Check with the modem's owner manual to understand the status lights on the modem.
4. After the modem has initialized, power-up the Extreme. Let this go on for, at least five minutes or until the AirPort's status LED is slowly blinking amber.
5. Using the AirPort Utility on a Mac or PC, configure the Extreme, as appropriate, for your network.

Ref:

• Set up a new base station using AirPort Utility on Mac - Apple Support
• AirPort - Complete Power Recycle - Apple Community

You're very welcome! I'm glad you got it worked out.