I use fresh Fedora 25 Workstation.
I am practicing in network configuring and found trouble. After some time starting/stopping/restarting NetworkManager to test my configuration files, it (systemd) started to show when I issue:
systemctl status NetworkManager
Some not important log info:
Failed to start NetworkManager NetworkManager.service: Unit entered failed state NetworkManager.service: Failed with result 'exit-code'. NetworkManager.service: Service hold-off time over, scheduling restart Stopped Netwok Manager. NetworkManager.service: Start request repeated too quickly. Failed to start Network Manager. NetworkManager.service: Unit entered failed state. NetworkManager.service: Failed with result 'start-limit-hit'.
"start-limit-hit" and "repeated too quickly" have some mystery in them. Extensive web searching does not give any relevant solutions.
mask/unmask of network.service does not help either.
systemctl start/stop network commands work without a hitch.