Delete button not working on Follow-Up Tracking Tool window

Howdy,
In response to a recent Zoom meeting invitation sent to our guests list, three of the following messages were received by me as admin:
<e-mail address> appears to be an invalid or non-working recipient email address. (One Advertised SMTP server permanently refused mail.)
I opened the Follow-Up Tracking Tool to review contact history (no problem), and, after our VPM said these folks had indicated via telephone they were no longer interested, I attempted to delete them. The little trash can icon has rollover and title working, but cliciking it doesn't do anything. The individual can, however, be deleted by selecting him on the Guests list screen then using the Delete People option.
Arthur