Complete the following steps.
sudo service tor@default reload
Check Tor's daemon status.
sudo service tor@default status
It should include a a message saying.
Active: active (running) since ...
In case of issues, try the following debugging steps.
Check Tor's config.
sudo -u debian-tor tor --verify-config
The output should be similar to the following.
Sep 17 17:40:41.416 [notice] Read configuration file "/usr/local/etc/torrc.d/50_user.conf".
Configuration was valid