Do you have SSO enabled and user directory lookup configured?

See help documentation on user directory lookup with tasks. https://help.nintex.com/en-us/nwc/content/designer/Actions/AssignaTasktoMultipleUsers.htm

You say you tried extracting the value but it failed?  That’s odd.  It should allow you to extract it by looping through the collection.  It works for me with this simple loop--

Can you send a few screenshots of your attempt to extract it?

Yes through MS Entra/AAD

You say you tried extracting the value but it failed?  That’s odd.  It should allow you to extract it by looping through the collection.  It works for me with this simple loop--

Can you send a few screenshots of your attempt to extract it?

Hmm, no didn’t fail to extract the e-mail from the people record selected (though I tried doing it through updating a hidden field in the initial form).  That succeeded, but it gave another error about not being assignable - perhaps because auth is turned on for the task assignee.

You say you tried extracting the value but it failed?  That’s odd.  It should allow you to extract it by looping through the collection.  It works for me with this simple loop--

Can you send a few screenshots of your attempt to extract it?

I tried this approach and now it’s not parsing the e-mail out of the collection.  Looping on the collection (though people picker is not set to multi so only returning one record?).  It shows the e-mail loading properly as text in a textbox in the form itself (extracted with rule/formula).

So I managed to solve this by storing the e-mail as a form variable and calling it directly.  None of the other methods seemed to work.  Also appears using a rule to update a hidden text field value doesn’t fire, which is why the text field method wasn’t working.

Still unclear why a people picker collection in NAC form won’t natively work in NAC workflow task assignment objects.