First, using -v2 to increase the verbosity will show you instantly the issue:
parse: warning: invalid section name: Main}
If you use the latest version of 66, you can simplify your service
[Main]
Type = classic
Description = "wpa_supplicant wifi autoconnetcion daemon"
[Start]
Execute = ( /usr/bin/execl-cmdline -s { /usr/bin/wpa_supplicant ${Args} } )
[Environment]
Args=!-B -c /etc/wpa_supplicant/wpa_supplicant.conf -i wlp0s20f
Even description is not mandatory anymore if you want.
winter It would be good if the Obarun wiki had an article about writing own simple services
you're right.