How do you restart the network service on Fedora 30?

Instead of systemctl, use NetworkManager, either via the GUI interface or the nmcli command-line.

Command Line

1. List the network interfaces on the system (as root):

# nmcli device
DEVICE      TYPE      STATE      CONNECTION         
eno1        ethernet  connected  Wired connection 1     
lo          loopback  unmanaged  --

Note the device name that you want to restart.

2. Then force the connection to reload:

# nmcli con reload eno1

(Substitute your device name for "eno1")

GUI

1. Open the 'Settings' application in Fedora.
2. In the left column, scroll down to 'Network'
3. Toggle the blue switch off and back on again for the connection to want to restart.