It seems that you haven't enabled Divide, which is why the sDiv slider is greyed out.
Please try the following steps:
1. GoZ character.
2. In Zbrush,go to Geometry > press" Divide".
3.Enable Layer Edit Mode
(if you can't click on REC, try adjusting the CC_Detail slider back and forth).
This should allow you to edit.
Reallusion Technical Support
email- tinateng@reallusion.com