I had a 2008 DS for 10 years with those
locks. There is a magnetic proximity
switch behind each lock arm. They both
have to be engaged before the slideout
motor gets power. If the arms retract and
the slideout doesn't move try tapping the
arms with a hammer to engage the proximity switch. If that doesn't work tap harder,you can't hurt anything. If that does work, the switch isn't normally making contact with the arms retracted as it should. Lubing the arms might help.
2017 Dutch Star 40ft. Freightliner chassis
My 10th motorhome in 43 years.