Change your settings for trusted computers
Your iOS device remembers the computers you've chosen to trust.
If you don't want to trust a computer or other device anymore, change the privacy settings on your iPhone, iPad, or iPod touch. Go to Settings > General > Reset > Reset Location & Privacy. Now when you connect to formerly trusted computers, the Trust alert will ask you whether you trust that computer.
Get help
If you tap Trust or Don't Trust but iOS doesn't accept your answer, or if the Trust alert won't appear, follow these steps. Try again after each:
- Make sure that your computer has the latest version of iTunes.
- Disconnect and reconnect your iOS device from your computer.
- Restart your iOS device and your computer.
- Reset your Trust settings.
If the above steps don't help, go to Settings > General > Reset and tap Reset Network Settings. This also resets Wi-Fi networks and passwords, cellular settings, and VPN and APN settings that you’ve used before.
If you downloaded iTunes for Windows from the Microsoft Store, make sure that iTunes Mobile Device Helper is enabled as a startup item.
If you still need help, contact Apple Support.
https://support.apple.com/en-us/HT202778