Will I lose anything if I reset network settings?
Resetting network settings would remove all stored Internet and networking-related data on the devices. Information about VPN, Ethernet, Bluetooth, cellular could be erased in the process of resetting. Fortunately, settings like hotspot, wireless display, and AirDrop (on iOS) will be untouched.
What happens after resetting network settings on iPhone?
After a reset, your iPhone reconnects to your carrier, and you must manually reconfigure the Wi-Fi and VPN settings. Alternatively, toggle Airplane Mode, restart your device, then reconnect to the network to see if it fixes your problem.