help for update group

[Brad Ching]

Hello:    I update redhat from 7.2 to 8.0 yesterday.But i find i can not use chgrp command to change folders or files group.And always tell me not find group name in group file. In fact i create all group that i need in redhat7.2 and use it very well.Who know have any problem for redhat8.0 group when i update . Pls tell me, thank you very much!