If the highlighting is not readily available in the current view, a prompt suggesting the user Disable CSS will display. The Disable CSS button above the webpage preview turns off CSS and displays all webpage content expanded.
If the issue still is not highlighted, the issue may be specifically related to a non-visual HTML element. Check the corresponding Element Location if this is related to an Accessibility or Best Practice issue.
For further assistance locating the issue within the webpage, contact DubBot support via the in-app chat, make a Task and assign it to @DubBot Support, or email firstname.lastname@example.org.