How to bulk upload webinars attendee information after changing the Custom Questions

[huangtangtang]

After adding a new Custom Questions for a webinar,I found that I can not bulk upload attendee information as I did before.

How can I bulk upload attendee information like this⇓？

・first name 

・last name

・mail address

・a Custom Question I created

[rajgarhiagautam]

Have you found a solution for this requirement?