The first picture is the plug, look closely how it locks the switch in. The second picture is how it retains the switch.

Check for debris within the switch space. Temporarily relocate the switch and check that it functions correctly, you should see the pins contacting the volume/power ribbon switches. If not you may have another issue.

Refit the switch by depressing it on the retaining side and and push the retaining plug back in (making sure it is orientated correctly)

Make sure the plug is now located properly within the midframe and that the switch functions correctly.