Yahoo!, and Yahoo! based mail systems such as AOL and AT&T, are currently not properly displaying the contents of confirmation emails.
HOW TO RESOLVE:
Until Yahoo! corrects this behavior you can approve the messages with one of the following options:
OPTION 1. You can approve a message from the Listserv interface. Instructions can be found here: https://support.goarch.org/-/confirming-listserv-messages
OPTION 2. Messages can be confirmed by replying to the confirmation email with simply “OK” in the body (without the quotation marks).
OPTION 3. If you select the meatball menu in the Yahoo! mail client, and click ‘view raw message’, you may be able to view the link and click it.