It could be the case that one of the applications in the group is still processing. You can
check the individual applications by searching for the details individually. To do that you
would need the passport numbers, dates of birth, full names and nationalities of all the
people in your group. If you have all that information at hand then you can check the
status of the people in your group individually.
ESTA applications can take up to 72 hours to process through, and there may be a few
details to double check before any confirmations are sent out. If one of your group
members is pending - just check back on the application after the 72 hours have passed.
Any pending applications will not stall those applicants in the group that have already
gotten a response, and those who have had their application approved can use ESTA to travel.
You can apply as a group of a maximum of 50 people, and you do not need to travel all
together! The person assigned as the group contact will receive the information of the
application and they need to be 18 years old or over. The group contact can also add or
remove applicants from the group.