I looked at your screenshots and I see you do have an enemies array setup for the map.
Highlighted is the default enemies which I see you have configured. On my end I have also setup region enemies without modifying the code:
Enemies do spawn normally in which I get two slimes.
The code error comes from using the spawn enemy function which has a different line up on my end.
Are you using the latest version of the plugin? I did a series of rapid updates recently.
