The name > org.freedesktop.PolicyKit1 was not provided by any .service files

I just had the same return when installing deluged on arch, I typed:

 systemctl start deluged

I tried with sudo and it worked fine. Seems to be a group permissions issue.

All I did was enable permissions for my user account and then typed:

 sudo systemctl start deluged

worked like a charm.

To clarify and summarize SNP22's post: You probably just forgot sudo.:

sudo systemctl [...]

Absolutely misleading warning ...