You forgot to trust the certificate. Go to Settings > General > VPN & Device Management to fix this.
Open AltServer on your computer. Connect your iOS device to the PC/Mac via USB, trust the computer, and enable "Sync with this iPhone over Wi-Fi" in iTunes or Finder. Click the AltServer icon in your computer's taskbar (or menu bar), select Install AltStore , and choose your connected iOS device. install ipa file without jailbreak