Thanks a lot for your post !
I had the same problem and couldn't understand ... As you, I commented the line "After" and it works ...
Why ? By now, I don't know ... multi-user.target means that the systemd-service will start when the system reach runlevel 2 ... I don't know why this line is here ...

After=network.agent should make sense , but I don't even need to put it
Multi-user .. I don't understand why it should be necessary ???

Anyay, it works ... 😊