You may simply be able to solve the problem by restarting FTL using one of these commands
service pihole-FTL restart
systemctl restart pihole-FTL
You can also view FTL's debugger using these instructions, which may offer some clues.
We generally want to know if FTL is not doing what it is supposed to, so if the above commands do not offer any solution or insight, please get in contact with us.
Update FYI: after [pihole -up] hit " Error: Unable to get latest release location from GitHub" etc, then [sudo service pihole-FTL restart] & [sudo systemctl restart pihole-FTL, still the same problem repeats. But rebooting the RPI3 completely then allowed [pihole -up] to run to completion.