This shows the location of the main Canon plug (under floor steel panel), and some photos taken at the top of the door (when closed)

These proximity switches detect that the latches are closed. The latches rotate into position a large metal “pointer” is sensed by these switches.

Did some testing, at the large Canon plug, measured continuity between pins A and B. On no-stow, continuity measured between A and B. When pushing the switch, which is the Stow position, continuity NOT measured. This is the expected result, but no EICAS message indicates in the cockpit console.

Wild guess, but thinking that the warning for a failure to Stow the Door Handle may not be configured to display this warning. It may be a configurable option.