Hey there, Dbadri17
Welcome to Apple Support Communities! It looks like you’re unable to activate your iPhone and receive a message that the activation server could not be reached. I’d be happy to help!
I’d recommend starting out by following the steps listed in: If you can't activate your iPhone - Apple Support
This includes steps such as contacting your carrier to determine whether your SIM card may need to be replaced, and completing a recovery mode restore.
If you’re still unable to active your iPhone after completing those steps, Contact - Official Apple Support.
Have a great day!