Merge participants not available?

Hello!

We facilitated a webinar today and had several participants who had multiple listings in the Attendee pod. In the past, we've been able to select the duplicates and select Merge Users from the menu; however, today it was not available (see screenshots below). Any idea why this would be? Has this functionality been removed?

Just in case our Audio Conference settings have anything to do with whether the Merge Users option is available, here's what we have:

Any insight is appreciated!

Thank you!