Unable to activate iPad mini 4

You should check this article: If you can't activate your iPad - Apple Support. https://support.apple.com/en-us/HT201407

If your iPad is a cellular model, some have reported that temporarily removing the sim allows activation to complete.

Otherwise, 5 possible causes for that error message:

1] Activation server is actually down. Very rare occurrence, and of short duration when it

does happen. Solution - try again.

2] Your firewall and/or antivirus software are preventing the necessary connection. Solution -

temporarily disable your firewall and/or antivirus software until the activation completes.

3] computer being used for activation has been used to jailbreak an iOS device in the past.

Solution - use a different computer.

4] iPad has been jailbroken. Your favorite search engine may provide some direction, but jailbreaks often prevent

activations/updates from succeeding. Per Terms of Use for this forum, discussion of jailbroken iPads is

prohibited.

5] your region and/or timezone settings are inconsistent with your actual location. Solution - set region and/or timezone correctly.

If you are having difficulties with (re)activating your iPad, you may have greater chance of success if you connect your iPad to a PC (with iTunes installed) or a Mac (with iTunes or Finder - as appropriate for the installed version of macOS). Once connected to your computer, your iPad will be detected - and you should be able to activate using iTunes.

1. Make sure that you have the latest version of macOS or the latest version of iTunes.
2. Check that your computer has an Internet connection.
3. With the cable that came with your iPad, connect your iPad to your computer. Locate your device on your computer.
4. Wait while your computer detects and activates your iPad:

• If you see an alert that shows "Set up as New" or "Restore from Backup", it means your iPad is activated.
• If you get an error message that says the "activation information was invalid" or "activation information could not be obtained from the device", use recovery mode to restore your iPhone.

A restart of your WiFi Router and/or a change of DNS settings may be helpful.

To restart you home router, disconnect power - then wait at least 30 seconds before restarting. When you router has rebooted (which may take several minutes), force-restart your iPad:

• On an iPad with a Home button: Press and hold the top button and the Home button at the same time. When the Apple logo appears, release both buttons.
• On an iPad with Face ID: Press and quickly release the volume up button, press and quickly release the volume down button, then press and hold the top button. When the Apple logo appears, release the button.

For recommended DNS servers (configured at your home router and/or your iPad), you might choose one of the following Recursive DNS Providers (IPv4 and IPv6 addresses included below):

Quad9

9.9.9.9

149.112.112.112

2620:fe::fe

2620:fe::9

OpenDNS

208.67.222.222

208.67.220.220

2620:0:ccc::2

2620:0:ccd::2

Cloudflare+APNIC

1.1.1.1

1.0.0.1

2606:4700:4700::1111

2606:4700:4700::1001

Should it be necessary to escalate your issue to Apple Support, the quickest route to engaging with Apple Support will be via the  Get Support link at top-right of this page.

To manually configure DNS settings on your iPad or iPhone Settings…

Enter the Settings app on your iOS device, and select Wi-Fi. Tap the small "i" icon next to the name of the network that needs the DNS server details changed, scroll down, and tap Configure DNS. You can now add and remove DNS Server IP Addresses as required.

Using OpenDNS as an example:

Other DNS services that I suggested (Quad9 and Cloudflare) obviously use a different set of server addresses.