I loaded PortableApps and ClamWin on my Kanguru USB that has a write protect lock switch. When in normal read/write mode ClamWin works fine.

When in write protected lock mode then I get an error prompt from ClamWin and in window disables the scan menu items and buttons, so that virus scan is not possible.

Should I be doing something different?

this depends on how it's organized the portable clamwin (that is not in our control)
clamwin itself works fine in readonly but it needs temp dir writable, maybe the portable app
uses a dir in the usb key to handle temp files, you should ask to the author of the portable clamwin package

Here's a link to the ClamWin Portable site: https://portableapps.com/apps/utilities/clamwin_portable on the Web. There is a support page link there.

Regards,