Thanks for your help. Unfortunately, I have tried the same thing on various browsers (Chrome, Firefox, and Safari), each with the browse cache emptied. Still no luck. I've also emptied the Joomla cache several times. I have verified that the Virtuemart update has run to completion and the "Extensions: Manage" area shows version 3.2.15 (June 14, 2018) as the latest version.
Any other ideas?
FYI: We are using the latest versions: Joomla 3.8.11 and Virtuemart 3.2.15.