Hi @jchen1 ,
Do you want to save user profile in a collection?
Could you show me your collection of userEmails?
Have you checked your emails in userEmails in your talent?
I've made a similar test and found that you need to make a little change on your original formula.
Here's my test for your reference:
1)create userEmails collection:
ClearCollect(userEmails,["Phoebel@Wic....ft.com","Test5@W...rosoft.com"])

2)create userProfiles collection:
ClearCollect(
userProfiles,
ForAll(
userEmails.Value,
Office365Users.UserProfileV2(Value)
)
)
First(userEmails).Value only represents the first email in useremail collection. You just need to use fieldname Value in Office365Users.UserProfileV2 function.
ForAll(collection,Office365Users.UserProfileV2(fieldname)) represents you will perform Office365Users.UserProfileV2(fieldname) one by one record.
Then I will get a collection with user profiles.

Best regards,