Approval Email notification cannot send  out to the  members  of  a group .    For diagnosing purpose ,  in a request detail page ,   click "Email" button trying to send a request  email to  an individual contact  or a group (which this individual  contact belongs to) to test  :

1)  in "TO" field ,   input the individual contact's userid ,  it is able to resolve to the correct email address of this contact , so the request email can be sent out accordingly 

2)  However ,  in "TO" field ,  input the  group name  that this contact belongs to , it is somehow not able to resolve to the email address of each individual contact in the group  as it is supposed to    and it gets the error message  

When inputting  the contact's userid  in "TO" field ,  service catalog  identifies  it as a indivual contact   and then it will get the contact's email address from ca_contact table in MDB database .

However ,  when inputting the group name in "TO" field ,  service catalog identifies it as a group ,  and then it will query EEM about  the membership information of  this group and get each member's email address from EEM instead of the ca_contact table   here .   So ,  if the contact doesn't have correct email address also in EEM ,   catalog will not able to get the contact's  correct email from EEM and therefore cannot resolve the group name to its member's email address accordingly in "TO" field  .  

service catalog 14.1 , 12.9

Check and Make sure the contact has the correct email address information in EEM also  :    login EEM UI  as EiamAdmin ,  go to   Manage Identities ->  Users -> search and locate the contact ,   and make sure sure it has the correct email address there  .