System Service with `--user` not starting on reboot even though it is enabled

Question

I have a resilio sync service run per user, however it is not active after a fresh reboot:

user@raspberrypi:~ $ systemctl is-enabled --user resilio-sync
enabled
user@raspberrypi:~ $ systemctl status --user resilio-sync
● resilio-sync.service - Resilio Sync service
   Loaded: loaded (/usr/lib/systemd/user/resilio-sync.service; enabled; vendor preset: enabled)
   Active: inactive (dead)
     Docs: https://help.getsync.com/

The following systemd config file is being linked:

$ cat ~/.config/systemd/user/multi-user.target.wants/resilio-sync.service
[Unit]
Description=Resilio Sync service
Documentation=https://help.getsync.com/
After=network.target network-online.target

[Service]
Type=forking
Restart=on-failure
PIDFile=%h/.config/resilio-sync/sync.pid
ExecStart=/usr/bin/rslsync --config %h/.config/resilio-sync/config.json
ExecStartPre=/etc/resilio-sync/init_user_config.sh
ExecStartPost=/bin/sleep 1
UMask=0007

[Install]
WantedBy=multi-user.target

which looks to me like it should be running, as the default target is:

$ systemctl get-default
graphical.target

Any advise for debugging this further?