URGENT on Nas Celerra. I'm trying to add AD user to ACL for user home folder already existing for NT domain but I have this error message "the security ID structure is invalid"

Hi all

I have Nas Celerra. On this Nas I have CIFS folder Shared name userfolder.
This user folder contains all user of my NT domain, and all folder had the following ACL:
NTdomain\user : Change
NTdomain\domain admin : FC

I have a trust with NTDomain & ADDomain.

When I'm trying add
ADDomain\user on user folder I have the following error message:
Unable to save permission change on <user> on <userfolder>

thanks for your help