Theme Editor permanently lost after installation

I had a few problems with installation (checked too many firewall settings and got the dreaded 500), but am back up with a restored database and re-installed plugin.

The subject says it all. I now am not able to access “Editor” to edit any theme or other files.

Any suggestions on what I did wrong and how I can fix this?

https://www.ads-software.com/extend/plugins/all-in-one-wp-security-and-firewall/