Siri cannot find homekit accessory on iphone
I have a Wemo smart plug named "Bed Light." When I ask Siri to control this light on my iPhone, I get the response "Sorry I wasn't able to find anything like that this time." In contrast, Siri on my Apple Watch 4 and my iPad are able to control the light, as is the HomeKit app on my iPhone. I have tried rebooting the iPhone to no avail.
This used to work on my iPhone, and it is not clear when it stopped working.
Any ideas?
iPhone XS, iOS 12