Older Theme On New Cs-Cart, Theme Editor Error

On the themeforest.net page advertising the theme, the developers stated that it works with the newest release of CS-Cart. As some of you may know, the colorpicker.tpl and possibly other files were moved from frontend to backend (if memory serves), and the devs did not fix this. They are also not responding to my support requests even though I still have 4 months left.

Anyway, long story short, the Theme Editor throws the "ErrorOops, something went wrong. (Service temporarily unavailable.)" error when I try to edit the theme. Consequently, I can't add a favicon and had to hack together a custom HTML block to display the logo (which means all the email templates are still using Demo Store logo, and various other problems.

Does anyone know where to look when trying to fix this error? I pasted the colorpicker.tpl file into the directory I found on another thread, but that didn't work. I finally had everything running perfectly at some point last year after days of messing around, until my CS-Cart trial period ended and it returned everything back to default.

Any help is greatly appreciated.

Check server error logs. Detailed error message should be there