a popup window that keeps showing up on my iPhone screen.

Hello Abodoaa,

We would like to see how we can help you with this server error. Are you using a specific app when this error appears? Which iOS version are you currently running? Go to Settings > General > About for the version. If you restart the iPhone with the steps in this link, does the error appear: Restart your iPhone - Apple Support

"How to restart your iPhone X, 11, 12, 13, or later

1. Press and hold either volume button and the side button until the power-off slider appears.
2. 
3. 
   
4. Drag the slider, then wait 30 seconds for your device to turn off. If your device is frozen or unresponsive, force restart your device.
5. To turn your device back on, press and hold the side button (on the right side of your iPhone) until you see the Apple logo."

Get back to us with these details so that we have a better understanding of the issue, and we can go from there.

Cheers!