Notice: this information was written when Microthemer version 2 was current. On Dec 26th, 2014 version 3 was released with a completely new interface. Some of the information may be redundant, but as much of
the functionality remains the same in version 3 we haven't deleted this post.
Microthemer should work without error with every theme.
It sounds like it could be a permissions problem. Microthemer should automatically create config.json. If it’s having trouble loading that file, it probably didn’t have “write permission” to create it in the first place.
Would you be able to set the permissions on the
directory to 755 and then go to the Manage Themes page and then back to the Microthemer UI (that should trigger the script that tries to create the file)?
If that doesn’t work, would you mind setting up an Administrator account for me on the WordPress install your working on so that I can troubleshoot this further? You can send me the login details via our pre-sales form: https://themeover.com/support/pre-sales-enquiries/