Unable to save within the upfront editor

Every time I try to save any changes I've made to the theme, I receive the error message "there has been an error saving your changes" I've searched for a resolution on your support but the only thread I can find regarding this is:

https://premium.wpmudev.org/forums/topic/fixer-theme-gives-error-when-saving

I've tried to apply the changes the the .htaccess file and increasing the php.ini file size type

Thanks!