I have 13 Kasa smart plugs and when I say Alexa, turn on "xxxxx" it works fine, also the same when I say turn off, all except one. When I say, Alexa, turn on Kevs bed, for the heated under blanket, it switches on, but when I say, Alexa, turn Kevs bed off, it says "OK, here's Stringify- sorry, I'm having trouble accessing your Stringify skill right now"

Anyone know why all the others work perfectly exc this one, even though it turns on fine, just when I turn it off. 
I deleted the plug and put a new one in, but it's exactly the same. Help please !!!